THE formation of The Independent Group of MPs opens up the way towards a ground-breaking future merger with the Liberal Democrats to create a centrist alliance that could "reshape British politics," senior party sources have told The Herald.

As Westminster experienced another tumultuous day with three Conservative backbenchers breaking ranks and joining TIG, Sir Vince Cable said his party would “hold out the hand of friendship” to them.

He hinted at a possible electoral pact between the Lib Dems and the breakaway group, saying it would be "foolish" for them to stand candidates against each other.

But Lib Dem sources, who expressed excitement at the events of the last 72 hours, went further, suggesting when the time was right, consideration should be given to the creation of a new centrist force, which could have the potential to form a mainstream government.

“What has happened has massive potential for big change; change the country needs, which would be a move away from the tired old two-party system,” declared one senior party insider.

The Lib Dem sources made clear it was early days to talk of a full merger with TIG, particularly given the uncertainties around Brexit.

They also stressed how the party leadership would want to know what the “fundamental values” of the new grouping were beyond a shared opposition to Britain’s withdrawal from the EU.

But one backbencher explained that if the number of TIG MPs grew significantly to, say, 40 or 50 – and more are expected to join the new grouping in the days ahead - then it could provide the parliamentary numbers – the Lib Dems have only 11 MPs – while Sir Vince's party could help to supply the structure and the money for a new centrist alliance.

“British politics is broken. We want change. This could be the start of that change but, of course, we want to know if these people have the same ideas and values as us,” declared the Lib Dem insider, adding: “We could now have an opportunity to reshape British politics.”

Just hours after Joan Ryan left the Labour Party to become the eighth TIG MP, denouncing Jeremy Corbyn’s leadership and claiming anti-Semitism was “part of his politics,” three Remainer Tories opened up a new chapter in the story of the Brexit fall-out by resigning their party membership to join the new Westminster group.

Heidi Allen, Anna Soubry and Sarah Wollaston hit out at Theresa May's "disastrous" handling of Brexit as they quit to bring the total of TIG MPs to 11.

At a Westminster press conference, they made clear their concerns about the Prime Minister’s performance went far wider, accusing her of throwing away the modernisation agenda begun by David Cameron and allowing the party to be taken over by right-wing Brexit hardliners.

Ms Soubry said she would not stay in the Conservatives to "skirmish on the margins when the truth is the battle is over and the other side has won".

The Nottinghamshire MP said: "The right wing, the hardline anti-EU awkward squad that have destroyed every leader for the last 40 years are now running the Conservative Party from top to toe. They are the Conservative Party."

She urged "fellow One Nation Conservatives" and "like-minded Lib Dems" to "please, come and join us" by breaking away from their parties and joining TIG.

Ms Soubry accused a "purple Momentum" of hard-right "zealots" of trying to force out MPs on the Remain wing of the party through deselections.

Ms Allen, who represents South Cambridgeshire, said she believed "a significant number" of Conservative MPs were considering joining the trio in TIG.

Asked if she might one day rejoin the Tories, she replied: “If we do our job right, there won’t be a Tory Party anymore.”

Dr Wollaston, the MP for Totnes in Devon, bemoaned how the Conservatives were once the most trusted on the economy and business but were “now marching us to the cliff-edge of a no-deal Brexit".

In Downing St, Mrs May said she was “saddened” by the trio’s decision, stressing how she was determined that under her leadership the Conservative Party would “always offer the decent, moderate and patriotic politics that the people of this country deserve". But it emerged the PM had made no attempt to dissuade the trio, who dubbed themselves the “three amigos,” from their decision to resign.

Earlier, Tory grandee Kenneth Clarke said he could think of "half a dozen" Conservatives who might quit the party unless it changed direction, noting how Mrs May could face "quite a lot" of ministerial resignations unless she ruled out a no-deal Brexit.

But Lord Pickles, the former Conservative Party Chairman, said the trio’s expected move was “sad and ultimately a big mistake”.

Nicola Sturgeon suggested it was no surprise that people were seeking an alternative to the "broken, failed Westminster politics".

Speaking in Glasgow, the First Minister declared: "Both the Tories and Labour are imploding at the moment and that's because their leaderships are pandering to extremes."

Labour dismissed TIG as an “Establishment coalition based on the failed and rejected policies of the past: austerity; corporate tax cuts, privatisation".

Meanwhile, it emerged that Mr Corbyn and the Labour leadership had endorsed a proposal to recall MPs who, like the TIG members, had stood on a party manifesto but then resigned and disavowed its policies.

The Labour leader’s spokesman claimed it was "clearly the right, decent and democratic thing" for any MP to stand again for election if they had left the party on whose platform they were elected.

However, Tom Watson, the deputy leader, opposed the recall move, saying it "just looks spiteful".

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Today, the Corbyn-supporting pressure group Momentum announced it would hold mass canvassing events in the constituencies of TIG MPs to build support for Labour in the event of a by-election and to “inform constituents that their MP has left Labour and joined a coalition with former Tory MPs instead”.

Momentum explained that over the next few weeks events would take place in the seats of the eight former Labour MPs attended by celebrities and politicians.

Laura Parker, the group’s National Co-ordinator, said TIG was a “Blairite-Tory coalition,” which their constituents had not voted for.

She said: “These splinter group MPs ran in 2017 on a manifesto of public ownership, scrapping tuition fees and ending austerity. Now, working hand in hand with the Tories, they’ll revert back to an agenda of privatisation, deregulation and tax cuts for the wealthy.

“This is unfair, undemocratic and dishonest. If they care about their constituents rather than their own careers, they should step down and fight a by-election,” added Ms Parker.