diff --git a/.changeset/silent-clubs-roll.md b/.changeset/silent-clubs-roll.md
new file mode 100644
index 0000000000..c80f884331
--- /dev/null
+++ b/.changeset/silent-clubs-roll.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-permission-backend': minor
+---
+
+**BREAKING** Removed support for the legacy backend system, please [migrate to the new backend system](https://backstage.io/docs/backend-system/building-backends/migrating)
diff --git a/plugins/permission-backend/package.json b/plugins/permission-backend/package.json
index 0408fb7031..847feb9faa 100644
--- a/plugins/permission-backend/package.json
+++ b/plugins/permission-backend/package.json
@@ -51,7 +51,6 @@
     "test": "backstage-cli package test"
   },
   "dependencies": {
-    "@backstage/backend-common": "^0.25.0",
     "@backstage/backend-plugin-api": "workspace:^",
     "@backstage/config": "workspace:^",
     "@backstage/errors": "workspace:^",
diff --git a/plugins/permission-backend/report.api.md b/plugins/permission-backend/report.api.md
index 48395265f7..a9b7720c6f 100644
--- a/plugins/permission-backend/report.api.md
+++ b/plugins/permission-backend/report.api.md
@@ -3,41 +3,9 @@
 > Do not edit this file. It is a report generated by [API Extractor](https://api-extractor.com/).
 
 ```ts
-import { AuthService } from '@backstage/backend-plugin-api';
 import { BackendFeature } from '@backstage/backend-plugin-api';
-import { DiscoveryService } from '@backstage/backend-plugin-api';
-import express from 'express';
-import { HttpAuthService } from '@backstage/backend-plugin-api';
-import { IdentityApi } from '@backstage/plugin-auth-node';
-import { LoggerService } from '@backstage/backend-plugin-api';
-import { PermissionPolicy } from '@backstage/plugin-permission-node';
-import { RootConfigService } from '@backstage/backend-plugin-api';
-import { UserInfoService } from '@backstage/backend-plugin-api';
-
-// @public @deprecated
-export function createRouter(options: RouterOptions): Promise<express.Router>;
 
 // @public
 const permissionPlugin: BackendFeature;
 export default permissionPlugin;
-
-// @public @deprecated
-export interface RouterOptions {
-  // (undocumented)
-  auth?: AuthService;
-  // (undocumented)
-  config: RootConfigService;
-  // (undocumented)
-  discovery: DiscoveryService;
-  // (undocumented)
-  httpAuth?: HttpAuthService;
-  // (undocumented)
-  identity?: IdentityApi;
-  // (undocumented)
-  logger: LoggerService;
-  // (undocumented)
-  policy: PermissionPolicy;
-  // (undocumented)
-  userInfo?: UserInfoService;
-}
 ```
diff --git a/plugins/permission-backend/src/index.ts b/plugins/permission-backend/src/index.ts
index b6d3366d37..42ac600821 100644
--- a/plugins/permission-backend/src/index.ts
+++ b/plugins/permission-backend/src/index.ts
@@ -19,4 +19,3 @@
  * @packageDocumentation
  */
 export { permissionPlugin as default } from './plugin';
-export * from './service';
diff --git a/plugins/permission-backend/src/service/router.ts b/plugins/permission-backend/src/service/router.ts
index 83dc90a363..0759f6df3a 100644
--- a/plugins/permission-backend/src/service/router.ts
+++ b/plugins/permission-backend/src/service/router.ts
@@ -17,7 +17,6 @@
 import { z } from 'zod';
 import express, { Request, Response } from 'express';
 import Router from 'express-promise-router';
-import { createLegacyAuthAdapters } from '@backstage/backend-common';
 import { InputError } from '@backstage/errors';
 import { IdentityApi } from '@backstage/plugin-auth-node';
 import {
@@ -99,8 +98,7 @@ const evaluatePermissionRequestBatchSchema: z.ZodSchema<EvaluatePermissionReques
  * Options required when constructing a new {@link express#Router} using
  * {@link createRouter}.
  *
- * @public
- * @deprecated Please migrate to the new backend system as this will be removed in the future.
+ * @internal
  */
 export interface RouterOptions {
   logger: LoggerService;
@@ -108,9 +106,9 @@ export interface RouterOptions {
   policy: PermissionPolicy;
   identity?: IdentityApi;
   config: RootConfigService;
-  auth?: AuthService;
-  httpAuth?: HttpAuthService;
-  userInfo?: UserInfoService;
+  auth: AuthService;
+  httpAuth: HttpAuthService;
+  userInfo: UserInfoService;
 }
 
 const handleRequest = async (
@@ -194,14 +192,13 @@ const handleRequest = async (
  * Creates a new {@link express#Router} which provides the backend API
  * for the permission system.
  *
- * @deprecated Please migrate to the new backend system as this will be removed in the future.
- * @public
+ * @internal
  */
 export async function createRouter(
   options: RouterOptions,
 ): Promise<express.Router> {
-  const { policy, discovery, config, logger } = options;
-  const { auth, httpAuth, userInfo } = createLegacyAuthAdapters(options);
+  const { policy, discovery, config, logger, auth, httpAuth, userInfo } =
+    options;
 
   if (!config.getOptionalBoolean('permission.enabled')) {
     logger.warn(
diff --git a/yarn.lock b/yarn.lock
index 20037a1652..3f4f005a71 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -6980,7 +6980,6 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@backstage/plugin-permission-backend@workspace:plugins/permission-backend"
   dependencies:
-    "@backstage/backend-common": "npm:^0.25.0"
     "@backstage/backend-defaults": "workspace:^"
     "@backstage/backend-plugin-api": "workspace:^"
     "@backstage/backend-test-utils": "workspace:^"