He is a member of the Socialist Campaign Group – although this affiliation did not prevent him from nominating Gordon Brown (rather than John McDonnell) for the 2007 Labour Party leadership election. As a supporter of the Better Off Out campaign, Mitchell is a Eurosceptic and he opposes the Common Fisheries Policy. He supported Leave in the 2016 referendum on EU membership, and he has commented that 'the EU is a racket run at Britain's expense, a system bonding national elites together to ignore the people'.