diff --git a/job/tf-merge-watcher/update_reference_repo.sh b/job/tf-merge-watcher/update_reference_repo.sh
new file mode 100755
index 0000000..65fff79
--- /dev/null
+++ b/job/tf-merge-watcher/update_reference_repo.sh
@@ -0,0 +1,36 @@
+#!/bin/bash
+#
+# Copyright (c) 2019, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+set -e
+
+ci_root="$(readlink -f "$(dirname "$0")/../..")"
+source "$ci_root/utils.sh"
+
+declare -A repo_urls=(
+[pdcs-platforms/ap/tf-topics]="name=trusted-firmware url=$tf_src_repo_url"
+[trusted-firmware/tf-a-tests]="name=trusted-firmware-tf url=$tftf_src_repo_url"
+[pdswinf/ci/pdcs-platforms/platform-ci]="name=trusted-firmware-ci url=$tf_ci_repo_url"
+)
+
+project="${GERRIT_PROJECT:-$PROJECT}"
+eval "${repo_urls[$project]?}"
+ref_dir="$project_filer/ref-repos/$name"
+
+# Create/update reference repository.
+mkdir -p "$ref_dir"
+if [ ! -d "$ref_dir" ]; then
+	# Clone afresh
+	mkdir -p "$ref_dir"
+	git clone -q "$url" "$ref_dir"
+else
+	# Update master
+	cd "$ref_dir"
+	git fetch -q origin master
+	git reset -q --hard origin/master
+fi
+
+echo "Updated $name"