An ex-Tory MP who left the party for a breakaway group has said that the battle for the Conservative Party was “over” because hard-right Brexit extremists have won.

Anna Soubry, a former minister, said “the right wing, the hardline anti-EU awkward squad” was running the party from top to bottom.

Speaking hours after she announced her resignation from the Conservatives alongside Heidi Allen and Sarah Wollaston, the Broxtowe MP also launched a scathing attack on Theresa May, saying she had failed to reach out to moderate Tory MPs.

The three MPs will join the Independent Group established by seven Labour MPs on Monday. They will also be joined by former Labour MP Joan Ryan, who resigned from Jeremy Corbyn’s party on Tuesday night, meaning the new group now has 11 MPs.

Speaking at a press conference in Westminster, Ms Soubry said she had made the decision to resign after concluding that the “right-wing shift” in the Conservative Party was not reversible.

She said: “As my friend [ex-Labour MP] Chuka Umunna said on Monday, you don’t join a political party to fight and you don’t stay in it and skirmish in the margins when the truth is the battle is over and the other side has won.

“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 tail – they are the Conservative Party.”

Urging other Tory MPs ​and "like-minded Lib Dems" to "come and join us", she continued: “Dear friends and now former colleagues who share those one-nation values and principles will of course today deny it, but I believe in their heads and in their hearts they know it’s over.

“And the reason they know it’s over is because we lost the referendum and Brexit now defines and shapes the Conservative Party.”

In a lengthy attack on Ms May's leadership, Ms Soubry said the prime minister had pandered to Brexiteers in the European Research Group [ERG] while ignoring “mainstream Conservatives”.

She said: “When the prime minister lost [the vote on] her withdrawal agreement, she said she would reach out to build a consensus. Of course, she should have done that from the beginning of all of this, not at the eleventh hour.

“But in that spirit, the first people that she invited into No10 were the ERG – the very people who just weeks beforehand had called a vote of no confidence in her leadership and had delighted in calling out her failures to any passing microphone.”

In contrast, Ms Soubry said, ”mainstream Conservatives with a fine record of loyalty who have served at the highest level in government...are still waiting for a call”.

Which MPs defected to form Change UK? Show all 12 1 /12 Which MPs defected to form Change UK? Which MPs defected to form Change UK? Change UK Details on the individual MPs are in the following photos Reuters Which MPs defected to form Change UK? Heidi Allen Anti-Brexit MP for South Cambridgeshire resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Chuka Umunna MP for Streatham since 2010 and prominent People's Vote supporter PA Which MPs defected to form Change UK? Anna Soubry The prominent anti-Brexit MP for Broxtowe resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Luciana Berger MP for Liverpool Wavertree since 2010, resigned from the Labour Party over bullying and anti-semitism PA Which MPs defected to form Change UK? Sarah Wollaston Anti-Brexit MP for Totnes resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Joan Ryan MP for Enfield North resigned from the Labour party on February 19 citing its tolerance of a "culture of anti-Jewish racism" PA Which MPs defected to form Change UK? Ann Coffey MP for Stockport since 1992 Chris McAndrew / UK Parliament Which MPs defected to form Change UK? Gavin Shuker MP for Luton South since 2010 Getty Which MPs defected to form Change UK? Chris Leslie MP for Nottingham East since 2010 PA Which MPs defected to form Change UK? Mike Gapes MP for Ilford South since 1992 PA Which MPs defected to form Change UK? Angela Smith MP for Penistone and Stocksbridge since 2010

Ms Allen also hit out at Ms May's leadership of the Conservatives, saying serving as a Tory MP had left her "tired of feeling numb".

Criticising the government's welfare policies, the South Cambridgeshire MP said: "I believed I was part of a party who worked collaboratively, welcomed knowledge and had the empathy to feel, but I have slowly but surely realised that I am not.

"I can no longer represent a government and a party who can't open their eyes to the suffering endured by the most vulnerable in society - suffering that we have deepened while having the power to fix."

She said Ms May had been "bullied into submission by the ERG" and was "dragging the country kicking and screaming to the edge of a no-deal abyss".

Ms Allen also claimed that a "significant number" of MPs were considering quitting their parties to join the Independent Group.

She said: "Having the courage to do what you know is right is hard but are there a number of colleagues in all parties who are keen to join us? Absolutely, but everybody has to get there in their own time.

"I think everybody will get there in their own time but yes, we do believe there are a significant number of colleagues [considering joining]."

Rebel MPs from Independent Group arrive in Commons ahead of PMQs

Ms Wollaston, who chairs the Commons health committee, said Theresa May "simply hasn't delivered on the pledge she made on the steps of Downing Street to tackle the burning injustices in our society".

She added: "I think that what we now see is the party that was once the most trusted on the economy and business is now marching us to the cliff-edge of a no-deal Brexit."

Announcing their resignation in a letter to Ms May, the three MPs wrote: “Sadly the Conservative Party has increasingly abandoned these principles with a shift to the right of British politics.

“We no longer feel we can remain in the party of a government whose policies and priorities are so firmly in the grip of the ERG and the DUP.”