John Martin McDonnell is a British politician who served as Shadow Chancellor of the Exchequer from 2015 to 2020. He has been the Member of Parliament (MP) for Hayes and Harlington since 1997, representing the Labour Party until the whip was withdrawn and his suspension on 23 July 2024 as a result of voting to scrap the two child benefit cap. On the political left, McDonnell is a member of the Socialist Campaign Group.