Arron Banks has called on Nigel Farage to pull out of hundreds of general election seats by Friday.
The Leave.EU boss who, along with Mr Farage, was one of the 'Bad Boys of Brexit', has warned his former ally that he could split the vote and damage the chances of Britain leaving the EU at all if he doesn't stand aside.
He also said Leave.EU would be releasing an app that tells Brexiteers which candidates to support in every seat, if the Brexit Party does not pull out by Friday.
The app would urge Brexiteers to vote Conservative in almost every constituency.
Mr Banks has also called on the residents of three constituencies in Stoke-on-Trent to vote Tory.
Stoke-on-Trent has been dubbed the Brexit capital of Britain after almost 70 per cent of voters supported Leave in the 2016 Referendum.
Mr Banks' new app will tell residents to vote for the Conservatives in all three seats in the region, if they want to see Brexit happen.
A spokesman for Leave.EU told the Times: 'This app is ''back Brexit, back Boris''. We will tell Brexiteers the right candidates to back for Brexit.
'If that is against the Brexit Party then so be it. We have to get Boris a majority so we can get Brexit done.'
Mr Banks and his group have repeatedly called on Mr Farage to step aside and have accused his Brexit Party of being in danger of splitting the vote and thwarting Britain's ability to leave the EU.
Stoke-on-Trent candidates were some of the first to be announced by the Brexit Party in August, leading to Tory fears that the presence of Mr Farage's group could lead to a Labour win.
The Leave.EU app is expected to support Brexit Party candidates in about 40 seats where the Conservatives are 'no hopers'.
The Brexit Party, and leader Nigel Farage, have repeatedly insisted that Boris Johnson's deal is 'not Brexit'.
The Leave.EU app uses data from the 2017 and 2015 elections, as well as this year's European elections, to calculate which candidate Brexiteers should vote for in each seat.
Leave.EU adds that it will also factor in information on voting intentions submitted online.
This data will be update every other Friday, which may also lead to the recommended candidate for a seat changing.