diff --git a/.github/workflows/publish.yaml b/.github/workflows/publish.yaml
index fcb6bda7..01d9bda8 100644
--- a/.github/workflows/publish.yaml
+++ b/.github/workflows/publish.yaml
@@ -26,7 +26,22 @@ jobs:
         with:
           bundler-cache: true
 
+      - name: Check if new version to release
+        id: gem_version
+        run: |
+          gem_version=$(ruby -r rubygems -e "puts Gem::Specification::load('$(ls *.gemspec)').version")
+          echo "::set-output name=gem_version::$gem_version"
+
+          if git fetch origin "refs/tags/v$gem_version" >/dev/null 2>&1
+          then
+            echo "Tag 'v$gem_version' already exists"
+            echo "::set-output name=new_version::false"
+          else
+            echo "::set-output name=new_version::true"
+          fi
+
       - name: Publish
+        if: ${{ steps.gem_version.outputs.new_version }}
         env:
           RUBYGEMS_API_KEY: ${{ secrets.RUBYGEMS_API_KEY }}
           GEM: govuk_tech_docs
@@ -35,7 +50,7 @@ jobs:
 
           cat << EOF > ~/.gem/credentials
           ---
-          :rubygems_api_key: ${API_KEY}
+          :rubygems_api_key: ${RUBYGEMS_API_KEY}
           EOF
 
           chmod 0600 ~/.gem/credentials