Boris Johnson's deputy at the Foreign Office has said there could be a second referendum on Britain's exit from the European Union, plunging Theresa May's government deeper into chaos.

Sir Alan Duncan MP, a minister of state at the Foreign Office, said it would be "possible" for there to be a second referendum on the terms of the exit deal, although he would be no second vote on whether to leave.

The news came as it emerged that Britain might continue to pay money to the EU if a new customs "backstop" plan continues into 2021.