diff --git a/Frontend/CO.CDP.OrganisationApp.Tests/FtsUrlServiceTests.cs b/Frontend/CO.CDP.OrganisationApp.Tests/FtsUrlServiceTests.cs
index 6de546262..5f385fdb0 100644
--- a/Frontend/CO.CDP.OrganisationApp.Tests/FtsUrlServiceTests.cs
+++ b/Frontend/CO.CDP.OrganisationApp.Tests/FtsUrlServiceTests.cs
@@ -7,16 +7,31 @@ namespace CO.CDP.OrganisationApp.Tests;
 
 public class FtsUrlServiceTests
 {
+    private readonly Mock<ISession> _sessionMock;
     private readonly Mock<IConfiguration> _configurationMock;
     private readonly Mock<ICookiePreferencesService> _cookiePreferencesService;
     private readonly IFtsUrlService _service;
 
     public FtsUrlServiceTests()
     {
+        _sessionMock = new();
         _configurationMock = new Mock<IConfiguration>();
         _cookiePreferencesService = new Mock<ICookiePreferencesService>();
         _configurationMock.Setup(c => c["FtsService"]).Returns("https://example.com/");
-        _service = new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object);
+        _service = new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object, _sessionMock.Object);
+    }
+
+    [Fact]
+    public void BuildUrl_WhenFtsServiceOriginSessionIsSet_BaseServiceUrlOriginShouldBeSessionValue()
+    {
+        _sessionMock.Setup(s => s.Get<string?>(Session.FtsServiceOrigin)).Returns("https://example1.com/");
+        _configurationMock.Setup(c => c["FtsService"]).Returns("https://example2.com/");
+        var service = new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object, _sessionMock.Object);
+        CultureInfo.CurrentUICulture = new CultureInfo("en-GB");
+
+        var result = service.BuildUrl("test-endpoint");
+
+        result.Should().Be("https://example1.com/test-endpoint?language=en_GB&cookies_accepted=unknown");
     }
 
     [Fact]
@@ -24,7 +39,7 @@ public void Constructor_ShouldThrowException_WhenFtsServiceIsNotConfigured()
     {
         _configurationMock.Setup(c => c["FtsService"]).Returns((string?)null);
 
-        Action action = () => new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object);
+        Action action = () => new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object, _sessionMock.Object);
 
         action.Should().Throw<InvalidOperationException>()
             .WithMessage("FtsService is not configured.");
@@ -34,7 +49,7 @@ public void Constructor_ShouldThrowException_WhenFtsServiceIsNotConfigured()
     public void BuildUrl_ShouldTrimTrailingSlashFromBaseServiceUrl()
     {
         _configurationMock.Setup(c => c["FtsService"]).Returns("https://example.com/");
-        var service = new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object);
+        var service = new FtsUrlService(_configurationMock.Object, _cookiePreferencesService.Object, _sessionMock.Object);
         var endpoint = "test-endpoint";
         CultureInfo.CurrentUICulture = new CultureInfo("en-GB");
 
diff --git a/Frontend/CO.CDP.OrganisationApp.Tests/Pages/OneLoginTest.cs b/Frontend/CO.CDP.OrganisationApp.Tests/Pages/OneLoginTest.cs
index 40574616d..de4afbb14 100644
--- a/Frontend/CO.CDP.OrganisationApp.Tests/Pages/OneLoginTest.cs
+++ b/Frontend/CO.CDP.OrganisationApp.Tests/Pages/OneLoginTest.cs
@@ -1,4 +1,5 @@
 using CO.CDP.OrganisationApp.Authentication;
+using CO.CDP.OrganisationApp.Constants;
 using CO.CDP.OrganisationApp.Models;
 using CO.CDP.OrganisationApp.Pages;
 using CO.CDP.OrganisationApp.WebApiClients;
@@ -9,7 +10,9 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Logging;
+using Microsoft.FeatureManagement;
 using Moq;
 using System.Security.Claims;
 
@@ -24,6 +27,8 @@ public class OneLoginTest
     private readonly Mock<IOneLoginAuthority> oneLoginAuthorityMock = new();
     private readonly Mock<IAuthenticationService> authService = new();
     private readonly Mock<IAuthorityClient> authorityClientMock = new();
+    private readonly Mock<IFeatureManager> featureManagerMock = new();
+    private readonly Mock<IConfiguration> configMock = new();
     private const string urn = "urn:fdc:gov.uk:2022:7wTqYGMFQxgukTSpSI2GodMwe9";
 
     [Fact]
@@ -48,6 +53,45 @@ public async Task OnGetSignIn_WhenRedirectUrlProvides_ShouldReturnAuthChallangeW
             .Which.Properties!.RedirectUri.Should().Be("/one-login/user-info?redirectUri=%2Forg%2F1");
     }
 
+    [Fact]
+    public async Task OnGetSignIn_WhenOriginIsNotNull_ShouldSetSessionWithFtsServiceOriginKey()
+    {
+        configMock.Setup(c => c["FtsServiceAllowedOrigins"]).Returns("http://example1.com,http://example2.com");
+        featureManagerMock.Setup(f => f.IsEnabledAsync(FeatureFlags.AllowDynamicFtsOrigins)).ReturnsAsync(true);
+        var origin = "http://example1.com";
+        var model = GivenOneLoginModel("sign-in");
+
+        var result = await model.OnGetAsync("/org/1", origin: origin);
+
+        sessionMock.Verify(s => s.Set(Session.FtsServiceOrigin, origin), Times.Once);
+    }
+
+    [Fact]
+    public async Task OnGetSignIn_WhenOriginIsNotListedInConfiguration_ShouldNotSetSessionWithFtsServiceOriginKey()
+    {
+        configMock.Setup(c => c["FtsServiceAllowedOrigins"]).Returns("http://example1.com,http://example2.com");
+        featureManagerMock.Setup(f => f.IsEnabledAsync(FeatureFlags.AllowDynamicFtsOrigins)).ReturnsAsync(true);
+        var origin = "http://example3.com";
+        var model = GivenOneLoginModel("sign-in");
+
+        var result = await model.OnGetAsync("/org/1", origin: origin);
+
+        sessionMock.Verify(s => s.Set(Session.FtsServiceOrigin, origin), Times.Never);
+    }
+
+    [Fact]
+    public async Task OnGetSignIn_WhenAllowDynamicFtsOriginsFeatureIsDisabled_ShouldNotSetSessionWithFtsServiceOriginKey()
+    {
+        configMock.Setup(c => c["FtsServiceAllowedOrigins"]).Returns("http://example1.com,http://example2.com");
+        featureManagerMock.Setup(f => f.IsEnabledAsync(FeatureFlags.AllowDynamicFtsOrigins)).ReturnsAsync(false);
+
+        var model = GivenOneLoginModel("sign-in");
+
+        var result = await model.OnGetAsync("/org/1", origin: "http://example1.com");
+
+        sessionMock.Verify(s => s.Set(Session.FtsServiceOrigin, "origin"), Times.Never);
+    }
+
     [Fact]
     public async Task OnGetUserInfo_OnSuccessfulAuthentication_ShouldRetrieveUserProfile()
     {
@@ -320,7 +364,9 @@ private OneLoginModel GivenOneLoginModel(string pageAction)
             logoutManagerMock.Object,
             oneLoginAuthorityMock.Object,
             authorityClientMock.Object,
-            new Mock<ILogger<OneLoginModel>>().Object)
+            new Mock<ILogger<OneLoginModel>>().Object,
+            featureManagerMock.Object,
+            configMock.Object)
         { PageAction = pageAction };
     }
 }
\ No newline at end of file
diff --git a/Frontend/CO.CDP.OrganisationApp/Constants/FeatureFlags.cs b/Frontend/CO.CDP.OrganisationApp/Constants/FeatureFlags.cs
index 19e20fad1..54793e8aa 100644
--- a/Frontend/CO.CDP.OrganisationApp/Constants/FeatureFlags.cs
+++ b/Frontend/CO.CDP.OrganisationApp/Constants/FeatureFlags.cs
@@ -3,4 +3,5 @@ namespace CO.CDP.OrganisationApp.Constants;
 public static class FeatureFlags
 {
     public const string Consortium = "Consortium";
+    public const string AllowDynamicFtsOrigins = "AllowDynamicFtsOrigins";
 }
\ No newline at end of file
diff --git a/Frontend/CO.CDP.OrganisationApp/FtsUrlService.cs b/Frontend/CO.CDP.OrganisationApp/FtsUrlService.cs
index 1410bb96c..812cd5de2 100644
--- a/Frontend/CO.CDP.OrganisationApp/FtsUrlService.cs
+++ b/Frontend/CO.CDP.OrganisationApp/FtsUrlService.cs
@@ -7,10 +7,14 @@ public class FtsUrlService : IFtsUrlService
 {
     private readonly string _ftsService;
     private readonly ICookiePreferencesService _cookiePreferencesService;
+    private readonly ISession _session;
 
-    public FtsUrlService(IConfiguration configuration, ICookiePreferencesService cookiePreferencesService)
+    public FtsUrlService(IConfiguration configuration, ICookiePreferencesService cookiePreferencesService, ISession session)
     {
-        var ftsService = configuration["FtsService"] ?? throw new InvalidOperationException("FtsService is not configured.");
+        _session = session;
+        var ftsService = _session.Get<string?>(Session.FtsServiceOrigin)
+                            ?? configuration["FtsService"]
+                            ?? throw new InvalidOperationException("FtsService is not configured.");
         _ftsService = ftsService.TrimEnd('/');
         _cookiePreferencesService = cookiePreferencesService;
     }
diff --git a/Frontend/CO.CDP.OrganisationApp/Pages/OneLogin.cshtml.cs b/Frontend/CO.CDP.OrganisationApp/Pages/OneLogin.cshtml.cs
index 91e116114..230d8834a 100644
--- a/Frontend/CO.CDP.OrganisationApp/Pages/OneLogin.cshtml.cs
+++ b/Frontend/CO.CDP.OrganisationApp/Pages/OneLogin.cshtml.cs
@@ -9,6 +9,7 @@
 using Microsoft.AspNetCore.Authentication.OpenIdConnect;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.FeatureManagement;
 using System.Net;
 
 namespace CO.CDP.OrganisationApp.Pages;
@@ -22,16 +23,18 @@ public class OneLoginModel(
     ILogoutManager logoutManager,
     IOneLoginAuthority oneLoginAuthority,
     IAuthorityClient authorityClient,
-    ILogger<OneLoginModel> logger) : PageModel
+    ILogger<OneLoginModel> logger,
+    IFeatureManager featureManager,
+    IConfiguration config) : PageModel
 {
     [BindProperty(SupportsGet = true)]
     public required string PageAction { get; set; }
 
-    public async Task<IActionResult> OnGetAsync(string? redirectUri = null)
+    public async Task<IActionResult> OnGetAsync(string? redirectUri = null, string? origin = null)
     {
         return PageAction.ToLower() switch
         {
-            "sign-in" => SignIn(redirectUri),
+            "sign-in" => await SignIn(redirectUri, origin),
             "user-info" => await UserInfo(redirectUri),
             "sign-out" => await SignOut(),
             _ => Redirect("/"),
@@ -68,8 +71,19 @@ public async Task<IActionResult> OnPostAsync(string logout_token)
         return Page();
     }
 
-    private IActionResult SignIn(string? redirectUri = null)
+    private async Task<ChallengeResult> SignIn(string? redirectUri = null, string? origin = null)
     {
+        session.Remove(Session.FtsServiceOrigin);
+        if (!string.IsNullOrWhiteSpace(origin)
+            && await featureManager.IsEnabledAsync(FeatureFlags.AllowDynamicFtsOrigins))
+        {
+            var allowedOrigins = config["FtsServiceAllowedOrigins"] ?? "";
+            if (allowedOrigins.Split(",", StringSplitOptions.RemoveEmptyEntries).Contains(origin))
+            {
+                session.Set(Session.FtsServiceOrigin, origin);
+            }
+        }
+
         var uri = "/one-login/user-info";
         if (Helper.ValidRelativeUri(redirectUri))
         {
@@ -84,7 +98,7 @@ private async Task<IActionResult> UserInfo(string? redirectUri = null)
         var userInfo = await httpContextAccessor.HttpContext!.AuthenticateAsync();
         if (!userInfo.Succeeded)
         {
-            return SignIn();
+            return await SignIn(redirectUri);
         }
 
         var urn = userInfo.Principal.FindFirst(JwtClaimTypes.Subject)?.Value;
@@ -93,7 +107,7 @@ private async Task<IActionResult> UserInfo(string? redirectUri = null)
 
         if (urn == null)
         {
-            return SignIn();
+            return await SignIn(redirectUri);
         }
         await logoutManager.RemoveAsLoggedOut(urn);
 
diff --git a/Frontend/CO.CDP.OrganisationApp/Session.cs b/Frontend/CO.CDP.OrganisationApp/Session.cs
index 578770e63..166278ca8 100644
--- a/Frontend/CO.CDP.OrganisationApp/Session.cs
+++ b/Frontend/CO.CDP.OrganisationApp/Session.cs
@@ -8,6 +8,7 @@ public class Session(IHttpContextAccessor httpContextAccessor) : ISession
     public const string RegistrationDetailsKey = "RegistrationDetails";
     public const string ConnectedPersonKey = "ConnectedPerson";
     public const string ConsortiumKey = "Consortium";
+    public const string FtsServiceOrigin = "FtsServiceOrigin";
 
     public T? Get<T>(string key)
     {
diff --git a/Frontend/CO.CDP.OrganisationApp/appsettings.AwsIntegration.json b/Frontend/CO.CDP.OrganisationApp/appsettings.AwsIntegration.json
index 098242d82..f145844d8 100644
--- a/Frontend/CO.CDP.OrganisationApp/appsettings.AwsIntegration.json
+++ b/Frontend/CO.CDP.OrganisationApp/appsettings.AwsIntegration.json
@@ -4,6 +4,7 @@
     "DiagnosticPage": {
       "Enabled": false,
       "Path": ""
-    }
+    },
+    "AllowDynamicFtsOrigins": true
   }
 }
diff --git a/Frontend/CO.CDP.OrganisationApp/appsettings.json b/Frontend/CO.CDP.OrganisationApp/appsettings.json
index 2878d914b..0f19399bc 100644
--- a/Frontend/CO.CDP.OrganisationApp/appsettings.json
+++ b/Frontend/CO.CDP.OrganisationApp/appsettings.json
@@ -21,6 +21,7 @@
   "DataSharingService": "",
   "EntityVerificationService": "",
   "FtsService": "",
+  "FtsServiceAllowedOrigins": "",
   "OneLogin": {
     "Authority": "",
     "ClientId": "",
@@ -56,7 +57,8 @@
     },
     "SharedSessions": false,
     "Consortium": false,
-    "ContentSecurityPolicy": true
+    "ContentSecurityPolicy": true,
+    "AllowDynamicFtsOrigins": false
   },
   "CompaniesHouse": {
     "Url": "",