The troubled People’s Vote campaign is to begin spending a £1m election war chest this week despite a continuing internal feud in part about whether it should back more Labour candidates.

More than half of the anti-Brexit campaign’s staff are still on strike after the its chairman, Roland Rudd, sacked its chief executive, James McGrory, and its director of communications, Tom Baldwin, over strategy.

The campaign is, however, ploughing on with its attempt to influence the election by backing dozens of pro-EU MPs with thousand of pounds worth of funding. Despite its well-publicised infighting, the campaign says it has received £200,000 in donations in the last two days.

The first recipient is set to be the former attorney general, Dominic Grieve, who is standing as an independent in his Beaconsfield constituency following his expulsion from the Conservative party over Brexit.

Others receiving cash will be candidates on the People’s Vote list of 100 marginal seats where it plans to tell remain supporters to vote tactically. Opponents of the strategy say that in some of these seats the campaign has shifted away from backing Labour candidates based on polling from the Best for Britain campaign rather its own research.

The campaign’s official tactical voting recommendations are also due to be published this week.

Patrick Heneghan, the new chief executive of the People’s Vote, said the campaign would “strain every sinew to stop Boris Johnson getting a majority”.

“We will be encouraging voters to get out in record numbers and back the candidate in each constituency with the best chance of defeating the Conservatives provided, at minimum, they support a People’s Vote.”

The shadow foreign secretary, Emily Thornberry, who backs a second referendum, urged the campaign to act on its own data. She told the Observer: “This election, there will be a big tactical vote for Labour by those who want to stop Boris Johnson forcing his hard Brexit and a new era of austerity on our country. Liberal Democrat boasts that they can win hundreds of seats are not supported by the independent analysis done by the People’s Vote campaign.”

The Lib Dem leader, Jo Swinson, suggested talks over a “remain alliance” are continuing, after a report in the Sunday Times said a pact could be formed in up to 60 constituencies

Swinson said the numbers were not accurate, but the concept of an alliance still stands among parties who want to prevent Brexit.

In the Brecon and Radnorshire byelection in Wales the Greens and Plaid Cymru stood down for the Lib Dem candidate, Jane Dodds, who went on to win. The area voted almost exactly 52% leave to 48% remain.

The Lib Dems have already been announced that they will not field a candidate against Grieve in Beaconsfield.

The party has also called for the rules on leaders’ debates in elections to be written into law. This follows comments from Swinson that her exclusion from debate slots on prime time television was sexist.

In an interview with Sophy Ridge on Sunday on Sky News, she said: “If you look at the 2010 election and the run-up to that election, the Liberal Democrats were polling a similar amount as we are now, actually we are now much closer to the other parties in terms of the poll rating and in that election we had Gordon Brown, David Cameron and Nick Clegg. Spot the difference.”

Ed Davey, the Lib Dems’ deputy leader, said: “It should not be in the gift of any political party to decide whether the public deserve the opportunity to scrutinise those who seek to lead this country. That is why TV debates should be mandatory, and the format should be decided by an independent commission.

“The current situation in which the Labour and Conservative parties stitch up how debates work is utterly intolerable.”

Davey’s comments come after ITV’s decision that its leaders debate would be a head-to-head involving Jeremy Corbyn and Boris Johnson.

The Lib Dems have 19 seats in the current parliament. Swinson said: “I think it’s fair to say that in the vast majority of constituencies the party of remain that is going to be best placed to win that seat would be the Liberal Democrats but it is not universally the case.”