More than 5,000 people joined the Liberal Democrats on the day Theresa May called a snap general election, the party has said.
Announcing the rise in the party's supporters, leader Tim Farron said: “We have been planning for a snap general election for months”.
“We have candidates in place, a manifesto under review and a campaign plan aimed at getting the best result we can,” he added.
The party apologised to potential members on Twitter saying technical difficulties may have prevented them from joining.
The Lib Dems are seeking to make significant gains in June, after haemorrhaging support while in a coalition with the Conservative party and being reduced to just eight MPs in the 2015 election.
Former Lib Dem Business Secretary Vince Cable, who lost his south London seat in 2015, told The Independent he was planning to run for election in June.
The party has taken a pro-Europe stance and established itself as a party staunchly opposed to Brexit, a position it hopes will win them support.
In the wake of Ms May's announcement, Mr Farron said: "If you want to avoid a disastrous Hard Brexit. If you want to keep Britain in the single market. If you want a Britain that is open, tolerant and united, this is your chance.
"Only the Liberal Democrats can prevent a Conservative majority."
Meanwhile grassroots group Momentum claimed that more than 2,500 people had joined the Labour Party on the day of the announcement.
The Conservatives have not released up to date membership figures since 2013; they are estimated to have around 100,000 members.
Speaking about the surge in support for the Liberal Democrats, the party’s president, Sal Brinton, said: “This is a time when liberals must stand together, and people across the country are doing just that.
“The surge in our membership proves that the Liberal Democrats are seen as the real opposition to this Conservative Brexit Government.
“While Theresa May is seeking to divide the country, the Liberal Democrats are the only party fighting to keep Britain Open, Tolerant and United.”
Both Labour and the Liberal Democrats have said they will support a Commons vote on Wednesday that would trigger the general election.
Under the Fixed Term Parliament's Act 2011, passed by the Coalition, the next election is scheduled for 2020 but can be called earlier if two thirds of MPs vote in favour.