In 2014, Matthews took up a position as National Campaigns Director at Better Off Out. He led Better Off Out's campaign for Britain to leave the European Union, liaising with the official campaign (Vote Leave) as well as with Leave.EU and Grassroots Out. During this time, he supervised the production of leaflets, posters and other campaign materials as well as organising their distribution to the public in the run-up to the 2016 European Union membership referendum.