Should the party leaders’ debate fail to happen, the channel will cast its net wider — perhaps to include former PM Tony Blair

Channel 4 is plotting a rival Brexit TV debate featuring Tony Blair and Boris Johnson as negotiations over the showdown between Theresa May and Jeremy Corbyn descend into acrimony.

The prime minister has done a deal with the BBC to take on Corbyn in a debate next Sunday which would also feature a section where the pair are cross-examined by experts who hold different views on Brexit.

Labour has rejected that approach and agreed with ITV a programme where the two would quiz each other and face questions from moderator Julie Etchingham.

Yesterday, Corbyn called on the BBC and Downing Street to accept the ITV format if they wanted the debate to go ahead. He tweeted: “Theresa May said she wanted a head to head