The Liberal Democrats have set their sights on taking out some of the big beasts of Brexit including foreign secretary Dominic Raab in the 12 December general election, leader Jo Swinson has declared.

Internal polling for the pro-EU party suggests “seismic” shifts in Remain-backing seats suddenly making the Lib Dems competitive in swaths of London and its commuter belt which have been Conservative for decades, including constituencies like Mr Raab’s Esher and Walton.

Referring to the surprise defenestration of then-cabinet minister Michael Portillo, which was the highlight of many people’s election night in 1997, Ms Swinson told The Independent: “We could be in a situation where people are asking each other ‘Did you stay up for Raab?’”

The ambitious – and perhaps rather optimistic – prediction reflects on Ms Swinson’s determination to recover her party’s position after seeing the Lib Dems squeezed by both Tories and Labour in the opening weeks of the election campaign.

After being accused of hubris for pitching herself as a potential prime minister, the 39-year-old is now speaking less about a possible Lib Dem government and more about the party’s position as the most likely block to a majority Boris Johnson administration.

Although the Lib Dems trail in a distant third in today’s BMG poll for The Independent, on 18 per cent to Labour’s 28 and the Tories’ 41, Ms Swinson believes her party is better placed than Jeremy Corbyn’s to chip away at Conservative MPs.

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“If you look at the polling in places like Great Grimsby, it’s clear that Labour are not really managing to stand up to the Conservatives in their own seats, let alone think about winning new seats form the Conservatives,” she said.

“So it is down to the Liberal Democrats to make sure we don’t have a Boris Johnson majority delivering Brexit. If you want to stop Brexit, job number one is to make sure Boris Johnson doesn’t get a majority, because if he does, he will force his bad Brexit deal on the country.”

She made clear that if the Lib Dems held the balance of power after 12 December, they would use it to ensure that the UK is offered a Final Say referendum on Brexit.

And she appeared to indicate that this could include allowing Mr Johnson’s deal to get through parliament so long as it has a referendum attached.

Asked if this was an option, she replied: “Obviously if there’s a piece of legislation that comes forward to have a people’s vote on the issue of a Brexit deal, we are going to vote for a people’s vote. We said that in the last parliament and nothing has changed.”

While insisting the Lib Dems continue to mount a national campaign, Ms Swinson confirmed the party is focusing efforts on key target seats, including constituencies formerly held by her party across the southwest and in places such as Cheltenham, Cheadle, Hazel Grove, Leeds North West and Nick Clegg’s old stronghold of Sheffield Hallam, lost to Labour in 2017.

The Lib Dem leader visits a primary school in Cambridge (EPA)

But there are other seats that would once have seemed out of reach to the party but have potentially come into play because of the way that Boris Johnson’s drive for Brexit has unsettled a tranche of traditional Tory voters who value economic stability and support for business over separation from the EU.

Prominent among these are the wealthy London seats where the Lib Dems are standing high-profile defectors Chuka Umunna in Cities of London and Westminster, Sam Gyimah in Kensington and Luciana Berger in Finchley and Golders Green.

But Mr Raab’s Surrey seat is typical of another category of Tory fiefdoms in the affluent southeast which voted Remain in 2016, also including the constituencies of Brexit cheerleaders like Sir John Redwood in Wokingham, Chris Grayling in Epsom and Ewell and Steve Baker in Wycombe.

Constituency polling by Survation released by the party suggested the Lib Dems were within four points of Mr Redwood. And now another poll by the same company has suggested that Mr Raab’s commanding 39-point lead in 2017 has been cut to just nine, with Lib Dems leapfrogging Labour to record 36 per cent support to the foreign secretary’s 45.

Both polls were taken before the withdrawal of Brexit Party candidates, which will have boosted Tory chances. But Ms Swinson believes that if Remain-backing supporters of other parties rally tactically behind her candidates, some surprising upsets are not impossible.

Esher and Walton – which voted 58.4 per cent Remain in 2016 – was one of the first stops on her battlebus tour.

And she said: “We are getting a very warm response. We have a fabulous candidate there in Monica Harding and people in that constituency are very angry with Dominic Raab.

“I think there could be some potentially very interesting upsets on polling day. We could be in a situation where people are asking each other ‘Did you stay up for Raab?’”

Ms Swinson has led the Lib Dems into the most wide-ranging electoral pact in recent political history, where her party joined the Greens and Plaid Cymru in standing aside candidates to give a Remain party the best chance of winning.

But she rejected suggestions that she should have done the same to help Labour in places like Canterbury – where local Lib Dems tried to stop the party running against anti-Brexit MP Rosie Duffield – or Uxbridge and South Ruislip, where Boris Johnson is facing a challenge to his seat.

Despite their individual views, she said, “every Labour candidate is standing on a manifesto to negotiate a Brexit deal”

And she remained insistent that she was “not interested” in propping up either Boris Johnson or Jeremy Corbyn in power, as she does not regard either as fit to run the country.

Ms Swinson put her party’s current difficult position in the polls down to Nigel Farage’s “stitch-up” deal to stand down candidates in favour of Tories, which had turned the contest from a four-horse race to something closer to the traditional battle between Tories and Labour.