Nearly 5,000 people have joined the Liberal Democrats since the Brexit vote, party officials said yesterday, as Tim Farron sought to rebuild his party’s support base by pledging to fight the next election on a promise to restore the UK’s membership of the EU.

With Labour in turmoil over Jeremy Corbyn’s leadership and the Conservatives split between Brexit and Remain supporters, the Lib Dems are hopeful of attracting new support from disaffected pro-EU voters from across the political spectrum.

David Cameron’s resignation means that a new Tory Prime Minister will be in place by October, and may call a general election to cement their authority. Mr Farron said yesterday that while the Lib Dems respected the outcome of the referendum, voters should be offered the choice of a party fully committed to re-entering the EU.

Former independent London mayoral candidate Siobhan Benita was among the thousands to join the party in the past four days, saying that they now represented “the only true Remain party”.

Their staunchly pro-EU stance will create allies for the Lib Dems in both the Labour and Conservative parties, holding out the possibility of cross-party collaboration. However, senior Lib Dems are not considering any kind of merger with pro-EU elements of the larger parties.

The Lib Dems saw their vote share collapse at the last general election, as supporters deserted the party following its decision to go into coalition with the Conservatives. The party was left with just eight MPs but saw slight gains in English council elections earlier this year.

Mr Farron said: “We are the only party committed to a future for Britain at the heart of Europe.

“Naturally we respect the result of the referendum, but Brexit will hit livelihoods, homes and jobs. As the Brexit camp renounce their promises on the NHS and immigration before the slogans have even been peeled off their battle bus, it is now clear that the British people were told lie after lie.

“We have always believed our economy and place in the world is stronger in Europe and it is only right that we offer that as a choice to people at the next general election – whenever that might be.