Campbell was one of 36 Labour MPs to nominate Jeremy Corbyn as a candidate in the Labour leadership election of 2015 and one of a handful of Labour MPs to publicly support leaving the European Union. Campbell continued to support Brexit, and to vote against attempts to delay it, in subsequent parliamentary votes. He justified this by noting that "I am a leaver, and I always have been. MPs are elected, unlike the EU bureaucrats, and if people don't like how MPs vote then they can get rid of us and that's how it should work."