Nigel Farage’s Brexit Party vote would collapse and switch back to the Tories if Boris Johnson succeeded in taking the UK out of the EU by October 31, a poll of Tory party members shows.

The vast majority of Conservative switchers to the Brexit Party would come back to the Tories in a subsequent general election, leaving Mr Farage with a tiny rump, according to the survey by pollsters Orb International for the Telegraph.