Britain's Prime Minister Theresa May arrives for the Conservative Party Conference in Birmingham, Britain, September 29, 2018. REUTERS/Toby Melville

BIRMINGHAM, England (Reuters) - Prime Minister Theresa May accused critics of her plans to leave the European Union of “playing politics” with Britain’s future and undermining the national interest in an interview with the Sunday Times newspaper.

In another interview next to the one with her on the newspaper’s front page, her former foreign minister Boris Johnson pressed his attack of her so-called Chequers plan for Brexit, saying a proposal that Britain and the EU should collect each other’s tariffs was “entirely preposterous”.