The Liberal Democrats will offer voters the chance to reverse Brexit in a second referendum, its election manifesto will say.

Tim Farron said the manifesto would confirm his party’s policy that the final say over any Brexit deal struck by Theresa May should rest with “the people in a referendum”.

“It is still possible for the British people to stop a Hard Brexit and keep us in the Single Market,” the Lib Dem leader told The Independent.

“If they want, it will also be possible for the British people to choose to remain in the European Union. Democracy didn’t end on June 23 and the people must have their say over what comes next.

“Someone will have the final say over our new deal with Europe. It could be politicians or it could be the people. Liberal Democrats believe it should be the people in a referendum.”

The stance underlines Mr Farron’s determination that the Lib Dems will offer a distinct alternative to the Conservatives and Labour, who both insist Brexit is now inevitable.

Jeremy Corbyn hinted that the Labour manifesto might include a second referendum pledge, but this has since been ruled out.

Labour has instead focused on securing a ‘meaningful vote’ in the Commons, probably in late 2018, although Ms May – if still Prime Minister – has insisted defeat would not send her back to the negotiating table.

Mr Farron has already sought to undermine Tory claims that a vote for the Lib Dems risks a “coalition of chaos”, potentially also bringing together Labour, the Scottish National Party and Greens.

“There is no way we can countenance any kind of arrangement or coalition with the Conservative party and likewise with the Labour party led by Jeremy Corbyn,” Mr Farron said at the weekend.

Later, Mr Farron told ITV that he was ruling out any kind of post-election deal.

Asked if his party would prop up a minority government on an informal basis, he said: “No, because what is very clear at this moment is that we have an official opposition which has not been behaving like an alternative government but is not even behaving like an opposition.”

The Lib Dems are about to confirm that its astonishing membership surge has taken the party past the 100,000 mark - after 12,500 people joined since the snap general election was announced.

Reaching six figures will make the party bigger than it has been since the mid-1990s. It boasted 101,768 members in 1994.

More than 50,000 members have joined since last year’s European referendum and more than 67,500 since the 2015 General Election, officials say.

Mr Farron added that his party raised £1.6m in donations in the four days following the Prime Minister’s announcement last week.