Boris Johnson has been warned that the Tory revolt against him will not end unless he can deliver a crushing victory in a crunch confidence vote tonight.

The PM has sent a letter to MPs pleading for them to 'draw a line' under furious infighting, after he suffered a series of huge blows - including his own anti-corruption tsar quitting and rival Jeremy Hunt joining the coup bid. 

Backbench chief Graham Brady confirmed this morning that at least 54 MPs have asked for a full ballot, which will now happen between 6pm and 8pm. Mr Johnson is addressing the parliamentary party now and the results will be declared at 9pm.

The development raises the possibility that Mr Johnson's tenure could come to a crashing end less than three years after he won a stunning 80-strong Commons majority.

However, if half of the 359 eligible MPs back him in the secret vote in theory he is safe for a year - with some insurgents fearing they have moved too early ahead of key by-elections later this month.

Cabinet ministers have been insisting that a single vote is enough, but there are fears he will be doomed if he cannot get backing from two-thirds of the parliamentary party.