Boris Johnson is the only Tory leadership candidate capable of beating both Jeremy Corbyn and the Brexit Party, according to new polling which suggests he would win a crushing 140-seat majority for the Conservatives at the next general election if he was elected Prime Minister.

The findings come as Mr Johnson launches his leadership campaign on Wednesday with the message that “delay means Corbyn”, warning Conservative colleagues the party will ‘kick the bucket’ if Brexit isn’t delivered by October 31.

In a further boost for Mr Johnson’s campaign, The Telegraph has learnt that three MPs who had publicly pledged support for his arch rival Michael Gove will switch to Mr Johnson in the wake of the Environment Secretary’s cocaine abuse confession.

They will be joined by Therese Coffey, a minister who serves under Mr Gove in the Department for Environment, Food and Rural Affairs, but who believes Mr Johnson would make a better leader.

The ComRes survey of more than 2,000 voters - commissioned by The Telegraph - put Mr Johnson way ahead of rivals with 27 per cent of the public agreeing he has what it takes to be a good prime minister compared with second placed Jeremy Hunt on 14 per cent.