Defeated Liberal Democrat leader Jo Swinson said she was proud that her party was the “unapologetic voice” of stopping Brexit in the election despite the strategy falling flat and losing her own seat.

Ms Swinson, the newest leader of any party heading into the election, lost her seat to the Scottish National Party blaming “a wave of nationalism” that had swept British politics north and south of the border.

She was ousted by just 149 votes in a loss to the SNP’s Amy Callaghan in East Dunbartonshire in a humiliating defeat and one of the biggest upsets of the election. She stepped down as leader soon afterwards, describing herself as “hugely disappointed” by the loss of her seat and the party’s performance.

The party won just 11 seats, falling one short of its lacklustre performance in the 2017 general election.

Video footage of SNP leader Nicola Sturgeon triumphantly cheering Ms Callaghan’s victory over Ms Swinson as she awaited a TV interview became one of the images of a dismal election for the Lib Dems.

The party’s campaign pledge to revoke the article 50 Brexit process divided people because of its unilateral, anti-democratic approach, alienating people not just within the 17.4 million voters who backed Brexit but among the 16.1 million people who voted to remain in the EU in 2016.

The final humiliation for the Lib Dems came with the party’s failure to prise the final seat to be declared in the election – St Ives in Cornwall – from the Conservatives in a marginal seat fought out by the two parties.

The party suffered from confusion around the multitude of tactical voting groups, dividing the vote between Lib Dem and Labour challengers to the Tories and ultimately splitting the Remain vote.

In contrast, Boris Johnson and the Conservatives managed to unite the Leave vote with the party’s simple but effective “get Brexit done” campaign slogan that tapped into the country’s Brexit fatigue.

‘Unapologetic voice’

Speaking in London in the wake of the result, Ms Swinson (39) – the first woman and youngest person to hold the leadership of the party – said she had no regrets about the strategy.

“I did not shirk the debates and the phone-ins, I turned up to the interviews, and I stood up proudly for our beliefs. I am proud that the Liberal Democrats have been the unapologetic voice of Remain in this election giving people the chance to choose to stop Brexit,” she said.

“Obviously it hasn’t worked. And I, like you, am devastated about that. But I don’t regret trying – trying everything.”

Sir Ed Davey, the party’s deputy leader who held his seat in London, and Baroness Sal Brinton will become joint acting leaders of the Lib Dems ahead of a leadership election in the new year as the party embarks on a period of soul-searching after three poor elections since being in coalition with the Tories.

Ms Swinson was criticised by party members for running a presidential-style campaign by pitching herself as a potential prime minister at the head of a party with less than 2 per cent of the seats at Westminster.

Former Liberal Democrat deputy leader Simon Hughes said that “every single decision” taken by Ms Swinson since she became leader in July “has been the wrong decision”.

“Every strategic decision – they decided to go for revoking article 50, having ignored the referendum. They decided that they could argue that that was because we might be a majority government. Incredible, incredible – nobody believes it,” he said.

“Jo led the campaign on the basis that she could be the prime minister – incredible. Nobody believed it. She was almost unknown.”