diff --git a/.github/workflows/afternoon_seal_quotes.yml b/.github/workflows/afternoon_seal_quotes.yml
index 724b4002..93f4183f 100644
--- a/.github/workflows/afternoon_seal_quotes.yml
+++ b/.github/workflows/afternoon_seal_quotes.yml
@@ -24,4 +24,4 @@ jobs:
       - name: Afternoon Seal Quotes
         id: afternoon_seal_quotes
         run: |
-          ./bin/seal_runner.rb afternoon_seal_quotes
+          ./bin/seal_runner.rb gems
diff --git a/.github/workflows/gem_version_checker.yml b/.github/workflows/gem_version_checker.yml
new file mode 100644
index 00000000..082b9f2b
--- /dev/null
+++ b/.github/workflows/gem_version_checker.yml
@@ -0,0 +1,28 @@
+name: "Gem Version Checker"
+
+on:
+  workflow_dispatch: {}
+  schedule:
+    - cron:  '00 13 * * 3' # Runs at 13:00 UTC, Every Wednesday.
+
+env:
+  SEAL_ORGANISATION: alphagov
+  GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}
+  SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}
+
+jobs:
+  gem-version-checker:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+
+      - name: Gem Version Checker
+        id: gem_version_checker
+        run: |
+          ./bin/seal_runner.rb gems
diff --git a/.github/workflows/morning_seal_prs.yml b/.github/workflows/seal_prs.yml
similarity index 100%
rename from .github/workflows/morning_seal_prs.yml
rename to .github/workflows/seal_prs.yml
diff --git a/bin/seal_runner.rb b/bin/seal_runner.rb
index f579f27b..55f10c5d 100755
--- a/bin/seal_runner.rb
+++ b/bin/seal_runner.rb
@@ -1,5 +1,6 @@
 #!/usr/bin/env ruby
 
+require_relative '../lib/gem_version_checker'
 require_relative '../lib/seal'
 require_relative '../lib/team_builder'
 
diff --git a/lib/gem_version_checker.rb b/lib/gem_version_checker.rb
new file mode 100644
index 00000000..2af3084c
--- /dev/null
+++ b/lib/gem_version_checker.rb
@@ -0,0 +1,43 @@
+require "uri"
+require "net/http"
+require "json"
+require_relative "slack_poster"
+
+class GemVersionChecker
+  def print_version_discrepancies(gems)
+    gems.filter_map { |gem|
+      repo_name = gem["app_name"]
+      repo_url = gem["links"]["repo_url"]
+      rubygems_version = fetch_rubygems_version(repo_name)
+      if rubygems_version && change_is_significant?(repo_name, rubygems_version)
+        "<#{repo_url}|#{repo_name}> has unreleased changes since v#{rubygems_version}"
+      end
+    }.join("\n")
+  end
+
+  def fetch_rubygems_version(gem_name)
+    uri = URI("https://rubygems.org/api/v1/gems/#{gem_name}.json")
+    res = Net::HTTP.get_response(uri)
+
+    JSON.parse(res.body)["version"] if res.is_a?(Net::HTTPSuccess)
+  end
+
+  def files_changed_since_tag(repo, tag)
+    Dir.mktmpdir do |path|
+      Dir.chdir(path) do
+        if system("git clone --recursive --depth 1 --shallow-submodules --no-single-branch https://github.com/alphagov/#{repo}.git > /dev/null 2>&1")
+          Dir.chdir(repo) { `git diff --name-only #{tag}`.split("\n") }
+        else
+          puts "Warning: Failed to clone #{repo}"
+          []
+        end
+      end
+    end
+  end
+
+  def change_is_significant?(repo_name, previous_version)
+    files_changed_since_tag(repo_name, "v#{previous_version}").any? do |path|
+      path.start_with?("app/", "lib/") || path == "CHANGELOG.md"
+    end
+  end
+end
diff --git a/lib/message_builder.rb b/lib/message_builder.rb
index 90ff8da0..63dc1e9c 100644
--- a/lib/message_builder.rb
+++ b/lib/message_builder.rb
@@ -18,6 +18,8 @@ def build
       build_dependapanda_message
     when :ci
       build_ci_message
+    when :gems
+      build_gems_message
     else
       build_regular_message
     end
@@ -57,6 +59,30 @@ def build_ci_message
     Message.new(ci_message, mood: "robot_face")
   end
 
+  def build_gems_message
+    Message.new(gems_message, mood: "gem")
+  end
+
+  def gems_message
+    @message = all_govuk_gems.group_by { |gem| gem["team"] == team }.each do |team, gems|
+      GemVersionChecker.new.print_version_discrepancies(gems)
+    end
+
+    template_file = Pathname.new("#{TEMPLATE_DIR}/gem_alerts.text.erb")
+    ERB.new(template_file.read, trim_mode: "-").result(binding).strip
+  end
+
+  def all_govuk_gems
+    @all_govuk_gems ||= fetch_gems
+  end
+
+  def fetch_gems
+    res = Net::HTTP.get_response("https://docs.publishing.service.gov.uk/gems.json")
+    raise "HTTP request failed: #{res.code}" unless res.is_a?(Net::HTTPSuccess)
+
+    JSON.parse(res.body)
+  end
+
   def ci_message
     @repos = check_team_repos_ci.reject { |_, v| v }.keys
     return nil if @repos.empty?
diff --git a/lib/seal.rb b/lib/seal.rb
index 9b6742a0..c32271b3 100755
--- a/lib/seal.rb
+++ b/lib/seal.rb
@@ -38,6 +38,8 @@ def bark_at(team, mode: nil)
                 MessageBuilder.new(team, :ci).build if team.ci_checks
               when "seal_prs"
                 MessageBuilder.new(team, :seal).build if team.seal_prs
+              when "gems"
+                MessageBuilder.new(team, :gems).build if team.gems
               end
 
     return if message.nil? || message.text.nil?
diff --git a/lib/slack_poster.rb b/lib/slack_poster.rb
index d10c2dc9..d6c9b7ec 100644
--- a/lib/slack_poster.rb
+++ b/lib/slack_poster.rb
@@ -60,6 +60,8 @@ def assign_poster_settings
         [":#{@season_symbol}angrier_seal:", "#{@season_name}Angry Seal"]
       when "robot_face"
         [":robot_face:", "Angry CI Robot"]
+      when "gem"
+        [":gem:", "Gem Release Robot"]
       when "tea"
         [":manatea:", "Tea Seal"]
       when "charter"
@@ -103,6 +105,6 @@ def set_mood_from_team
   end
 
   def channel
-    @team_channel = "#bot-testing" if ENV["DEVELOPMENT"]
+    @team_channel = "#murilo-testing"
   end
 end
diff --git a/lib/team.rb b/lib/team.rb
index 306463ed..178facab 100644
--- a/lib/team.rb
+++ b/lib/team.rb
@@ -7,6 +7,7 @@ def initialize(
     afternoon_seal_quotes: nil,
     dependapanda: nil,
     ci_checks: nil,
+    gems: nil,
     compact: nil,
     exclude_labels: nil,
     exclude_titles: nil,
@@ -22,6 +23,7 @@ def initialize(
     @afternoon_seal_quotes = (afternoon_seal_quotes.nil? ? false : afternoon_seal_quotes)
     @dependapanda = (dependapanda.nil? ? false : dependapanda)
     @ci_checks = (ci_checks.nil? ? false : ci_checks)
+    @gems = (gems.nil? ? false : gems)
     @compact = (compact.nil? ? false : compact)
     @quotes_days = quotes_days || []
     @exclude_labels = exclude_labels || []
@@ -40,6 +42,7 @@ def initialize(
     afternoon_seal_quotes
     dependapanda
     ci_checks
+    gems
     compact
     exclude_labels
     exclude_titles
diff --git a/lib/team_builder.rb b/lib/team_builder.rb
index 2779ee16..95e67c1e 100644
--- a/lib/team_builder.rb
+++ b/lib/team_builder.rb
@@ -46,6 +46,7 @@ def build_all_teams
         raise "#{team_name} is a GOV.UK team and shouldn't list repos in ./config/alphagov.yml"
       end
       team_config["ci_checks"] = is_govuk_team?(team_name)
+      team_config["gems"] = is_govuk_team?(team_name)
       Team.new(**apply_env(team_config))
     end
   end
@@ -60,6 +61,7 @@ def apply_env(config)
       afternoon_seal_quotes: env["AFTERNOON_SEAL_QUOTES"] == "true" || config["afternoon_seal_quotes"],
       dependapanda: env["DEPENDAPANDA"] == "true" || config["dependapanda"],
       ci_checks: env["CI_CHECKS"] == "true" || config["ci_checks"],
+      gems: env["GEMS"] == "true" || config["gems"],
       compact: env["COMPACT"] == "true" || config["compact"],
       exclude_labels: env["GITHUB_EXCLUDE_LABELS"]&.split(",") || config["exclude_labels"],
       exclude_titles: env["GITHUB_EXCLUDE_TITLES"]&.split(",") || config["exclude_titles"],
diff --git a/spec/gem_version_checker_spec.rb b/spec/gem_version_checker_spec.rb
new file mode 100644
index 00000000..03565d5a
--- /dev/null
+++ b/spec/gem_version_checker_spec.rb
@@ -0,0 +1,53 @@
+require "./lib/gem_version_checker"
+
+RSpec.describe GemVersionChecker do
+  subject(:gem_version_checker) { described_class.new }
+
+  let(:slack_poster) { instance_double(SlackPoster, send_request: nil) }
+
+  before do
+    allow(SlackPoster).to receive(:new).and_return(slack_poster)
+  end
+
+  it "fetches version number of a gem from rubygems" do
+    stub_rubygems_call("6.0.1")
+
+    expect(gem_version_checker.fetch_rubygems_version("example")).to eq("6.0.1")
+  end
+
+  it "detects when there are no files changed since the last release that are built into the gem" do
+    stub_devdocs_call
+    stub_rubygems_call("1.2.3")
+    stub_files_changed_since_tag(["README.md"])
+
+    expect { gem_version_checker.print_version_discrepancies }.to output("team: #platform-security-reliability-team\n").to_stdout
+  end
+
+  it "detects when there are files changed since the last release that are built into the gem" do
+    stub_devdocs_call
+    stub_rubygems_call("1.2.2")
+    stub_files_changed_since_tag(["lib/foo.rb"])
+
+    expect { gem_version_checker.print_version_discrepancies }.to output(
+      "team: #platform-security-reliability-team\n<https://example.com|example> has unreleased changes since v1.2.2\n",
+    ).to_stdout
+  end
+
+  def stub_files_changed_since_tag(files)
+    allow(gem_version_checker).to receive(:files_changed_since_tag) do
+      files
+    end
+  end
+
+  def stub_rubygems_call(version)
+    repo = { "version": version }
+    stub_request(:get, "https://rubygems.org/api/v1/gems/example.json")
+      .to_return(status: 200, body: repo.to_json, headers: {})
+  end
+
+  def stub_devdocs_call
+    repo = [{ "app_name": "example", "team": "#platform-security-reliability-team", "links": { "repo_url": "https://example.com" } }]
+    stub_request(:get, "https://docs.publishing.service.gov.uk/gems.json")
+      .to_return(status: 200, body: repo.to_json, headers: {})
+  end
+end
diff --git a/templates/gem_alerts.text.erb b/templates/gem_alerts.text.erb
new file mode 100644
index 00000000..77a9d9e2
--- /dev/null
+++ b/templates/gem_alerts.text.erb
@@ -0,0 +1 @@
+<%= @message %>