He then became an advocate for the UK remaining in a Customs Union with the European Union, and voted with the Labour Party for a Customs Union amendment in the House of Commons. He continued to argue, following that defeat, that following the outcome of the referendum "the Customs Union option was the best available – the only way of achieving the substantial separation desired by Brexit voters while remaining close to the EU diplomatically and economically." He proposed, however, following the failure of parliament to reach any positive agreeement – that the issue could be passed to a Citizens Assembly, chaired by the Archbishop of Canterbury to find a compromise on Brexit.