diff --git a/.github/workflows/diff-change-to-package.yaml b/.github/workflows/diff-change-to-package.yaml
index 25466acfc8..4d76e337ec 100644
--- a/.github/workflows/diff-change-to-package.yaml
+++ b/.github/workflows/diff-change-to-package.yaml
@@ -1,11 +1,8 @@
-name: Diff changes to GitHub release
+name: Diff changes to npm package
 
 on:
-  pull_request:
-    paths: ['dist/**']
-
-permissions:
-  pull-requests: write
+  workflow_call:
+  workflow_dispatch:
 
 jobs:
   generate-diff:
@@ -32,15 +29,15 @@ jobs:
 
       - name: Generate diff
         run: |
-          # Using `origin/$GITHUB_BASE_REF` to avoid actually checking out the branch
-          # as all we need is to let Git diff the two references
-          bin/dist-diff.sh origin/$GITHUB_BASE_REF $GITHUB_WORKSPACE
+          git config user.name github-actions
+          git config user.email github-actions@github.com
+          bin/package-diff.sh $GITHUB_BASE_REF $GITHUB_WORKSPACE
 
-      - name: Save GitHub release diffs
+      - name: Save npm package diffs
         uses: actions/upload-artifact@v3.1.3
         with:
-          name: GitHub release diffs
-          path: .cache/diff/dist/*.diff
+          name: Package diff
+          path: .cache/diff/package/*.diff
           if-no-files-found: ignore
 
       - name: Add comment to PR
@@ -56,19 +53,19 @@ jobs:
 
             const diffs = [
               {
-                path: '${{ github.workspace }}/.cache/diff/dist/js.diff',
-                titleText: 'JavaScript changes to GitHub release',
-                markerText: 'dist/js.diff'
+                path: '${{ github.workspace }}/.cache/diff/package/js.diff',
+                titleText: 'JavaScript changes to npm package',
+                markerText: 'package/js.diff'
               },
               {
-                path: '${{ github.workspace }}/.cache/diff/dist/css.diff',
-                titleText: 'Stylesheets changes to GitHub release',
-                markerText: 'dist/css.diff'
+                path: '${{ github.workspace }}/.cache/diff/package/css.diff',
+                titleText: 'Stylesheets changes to npm package',
+                markerText: 'package/css.diff'
               },
               {
-                path: '${{ github.workspace }}/.cache/diff/dist/other.diff',
-                titleText: 'Other changes to GitHub release',
-                markerText: 'dist/other.diff'
+                path: '${{ github.workspace }}/.cache/diff/package/other.diff',
+                titleText: 'Other changes to npm package',
+                markerText: 'package/other.diff'
               }
             ]
 
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index ff97f72280..65ddccf9a0 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -303,6 +303,17 @@ jobs:
     uses: ./.github/workflows/screenshots.yml
     secrets: inherit
 
+  generate-diff-package:
+    name: Diff changes to npm package
+    needs: [install]
+
+    permissions:
+      pull-requests: write
+
+    # Run existing "Diff changes to npm package" workflow
+    # (after only install has been cached)
+    uses: ./.github/workflows/diff-change-to-package.yaml
+
   generate-stats:
     name: Stats comment
     needs: [install]
diff --git a/bin/package-diff.sh b/bin/package-diff.sh
index 52aa881088..7a7bef7452 100755
--- a/bin/package-diff.sh
+++ b/bin/package-diff.sh
@@ -1,33 +1,54 @@
 #!/bin/sh
 set -ex
 
-# Computes the diff of `dist` between a provided base reference (branch, tag, commit SHA) and the current HEAD.
+CURRENT_BRANCH_NAME=$(git rev-parse --abbrev-ref HEAD)
+
+# Computes the diff of `packages/govuk-frontend/dist` between a provided base reference (branch, tag, commit SHA) and the current HEAD.
 # It outputs the resulting diff in the provided output folder
 #
-# Usage: `bin/dist-diff.sh <base-reference> <output-folder>`
+# Usage: `bin/package-diff.sh <base-reference> <output-folder>`
 
 # Default the base branch to main to allow running locally quickly
 base="${1:-main}"
 # And the output folder to the current working directory
 output_folder="${2:-`pwd`}"
 
-rm -Rf .cache/diff/dist
-mkdir -p .cache/diff/dist/base
-mkdir -p .cache/diff/dist/head
+rm -Rf .cache/diff/package
+mkdir -p .cache/diff/package
+
+# Switch to base branch
+git checkout $base
+
+# Build package for base branch
+npm install --ignore-scripts --no-save --silent
+npm run build:package --ignore-scripts
+
+# Switch back to original branch
+git checkout $CURRENT_BRANCH_NAME
+
+# Commit build output from base branch
+git add --force packages/govuk-frontend/dist/
+git commit -m "Build output for '$base'" --no-verify
+
+# Build package for original branch
+npm install --ignore-scripts --no-save --silent
+npm run build:package --ignore-scripts
+
+# Commit build output from original branch
+git add --force packages/govuk-frontend/dist/
+git commit -m "Build output for '$CURRENT_BRANCH_NAME'" --no-verify
 
 # Diff the minified JS file
-git diff \
-  $base:dist/govuk-frontend-$(git show $base:dist/VERSION.txt).min.js \
-  dist/govuk-frontend-$(cat dist/VERSION.txt).min.js \
-  > $output_folder/.cache/diff/dist/js.diff
+git diff HEAD^ -- packages/govuk-frontend/dist/govuk/govuk-frontend.min.js \
+  > $output_folder/.cache/diff/package/js.diff
 
-# Diff the minified CSS file
-git diff \
-  $base:dist/govuk-frontend-$(git show $base:dist/VERSION.txt).min.css \
-  dist/govuk-frontend-$(cat dist/VERSION.txt).min.css \
-  > $output_folder/.cache/diff/dist/css.diff
+# # Diff the minified CSS file
+git diff HEAD^ -- packages/govuk-frontend/dist/govuk/govuk-frontend.min.css \
+  > $output_folder/.cache/diff/package/css.diff
 
 # Diff the rest of the files, excluding the sourcemaps and the minified files
 # See https://git-scm.com/docs/gitglossary#Documentation/gitglossary.txt-aiddefpathspecapathspec
-git diff -M05 $base -- dist ":(exclude)dist/*.min.*" \
-  > $output_folder/.cache/diff/dist/other.diff
+git diff -M05 HEAD^ -- packages/govuk-frontend/dist \
+  ":(exclude)**/*.map" \
+  ":(exclude)**/*.min.*" \
+  > $output_folder/.cache/diff/package/other.diff