THE Liberal Democrats, Plaid Cymru and the Green Party have formed a General Election pact, agreeing not to stand against each other in 60 seats south of the border to bolster the chances of victory for Remain candidates.

The campaign group Unite to Remain brokered the deal and said it was confident "at least 44" of the 60 seats were "highly winnable".

Heidi Allen, the former Conservative-turned Change UK-turned Liberal Democrat MP, who chairs the group, pointed out how there was a “different dynamic” in Scotland, where the cross-party agreement does not apply.

The pact follows an agreement earlier this year in the Brecon and Radnorshire by-election, where the Lib Dems took the seat from the Conservatives after the other two parties stood aside.

Ms Allen, who previously represented South Cambridgeshire, said the cross-party arrangement was "unprecedented in modern British political history".

In total, the Lib Dems will stand in 43 constituencies, the Greens will stand in 10 and Plaid Cymru will stand in seven.

In the Isle of Wight and Brighton Pavilion, the Greens will be given a free run, while in the constituencies of Richmond Park, Guildford and Cheltenham, the Lib Dems will be unopposed by other Remain-backing parties.

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Jo Swinson, the Lib Dem leader, said she was "delighted" about the agreement, adding that it was a "significant moment for all people who want to support Remain candidates across the country".

Ms Allen, who is not standing in the election, explained: "I thought when I got into Parliament as an MP that not on everything, but on big issues that would really affect the country's future Parliament would work together, that the Government would reach out to the Opposition. And they just haven't done that at all.

"We've had two massive failures of leadership from the Conservative Party and from Labour."

Ms Allen said the Lib Dems, the Greens and Plaid were saying: "You know what? Enough. Somebody has to step up and offer proper leadership on Brexit."

She said there were three core issues which the parties shared views on: a second EU referendum; proportional representation and climate change.

"Secretly, I'm quite excited,” declared the former MP. “I hope that if this is successful, they'll look back and go: 'Do you know what guys? That worked pretty well. Shall we try that again?' Because we look at European politics, coalition-based progressive alliances. I'd love to see that here too."

At a press conference in London, Peter Dunphy, election strategist and a director at Unite to Remain, said: "At least 44 of those 60 can be regarded as highly winnable constituencies."

He said this evaluation was based on a wide range of data, including current national opinion polls, local election results and European elections.

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"These will be seats in which the parties will be putting huge resource because they believe that they can win those seats," he said.

On the issue of the Labour Party not being part of the pact, Baroness Brinton, the Lib Dem President, said: "First of all, Jeremy Corbyn stands for Brexit. This is about Remain. That's a fundamental block."

She added: "The second thing is Labour have made it plain that under their rules, they will never stand back for any other party. And that I'm afraid is part of the old two-party style of politics."

Plaid Cymru's Liz Saville Roberts said she hoped the parties coming together gave "some credibility" to politics. “Our message is clear: this is what matters to us and this is why we're acting this way."

Green MEP Molly Scott Cato said she hoped it would be seen as an "historic day" and that the deal would "break the two-party stranglehold".