In 2016, Pinkney signed a letter in "The Guardian" newspaper alongside Sean Hoyle, Paul McDonnell and John Reid from the National Union of Rail, Maritime and Transport Workers (RMT), which opposes the Electoral Commission choosing Leave.EU, Vote Leave or Grassroots Out as the official group advocating for the UK's withdrawal from the European Union in the 2016 referendum on the subject. The letter said that: We call on the commission not to give taxpayers' money to the Tory and Ukip-dominated Vote Leave, Leave.EU or Grassroots Out campaigns, or any amalgam of them ... We believe there are millions of trade unionists, young people, anti-austerity campaigners and working-class voters, whose opposition to the big business-dominated EU would not be represented by these organisations. ... We call on the Electoral Commission to recognise that a significant proportion of those who will vote against the EU do so because they support basic socialist policies of workers' rights, public ownership, and opposition to austerity and racism.