TORY turmoil at Westminster deepened when Boris Johnson lost his working majority with the defection of former minister Philip Lee, who crossed the House of Commons floor to join the Liberal Democrats.

The dramatic move made the Prime Minister’s task of rallying Conservative colleagues to his cause all the harder after he spent much of the day trying to convince some of them not to rebel in the vote on extending Brexit Day to January 31.

Mr Lee, a former Justice Minister, said the party that he had joined more than 27 years ago was not the party he was leaving now.

"This Conservative Government is aggressively pursuing a damaging Brexit in unprincipled ways,” declared the Berkshire MP, who accused it of deliberately using a strategy of political manipulation, bullying and lies.

"It is putting lives and livelihoods at risk unnecessarily and it is wantonly endangering the integrity of the United Kingdom. More widely, it is undermining our country's economy, democracy and role in the world,” he added.

Jo Swinson, the Lib Dem leader, welcomed Mr Lee to her party on social media, tweeting: "Welcome @DrPhillipLeeMP - you have joined us at the most crucial time. I look forward to working with you to prevent a disastrous Brexit and to fight for a fairer, more equal society."

Mr Lee made his dramatic move during Mr Johnson’s statement on the G7 summit, which was dominated by bitter exchanges on Brexit.

The PM, referring to the rebel extension bill, insisted he would never go and “beg” Brussels for a further delay to Britain’s withdrawal and "surrender" control of the Brexit negotiations to the EU27.

He told MPs: "It would enable our friends in Brussels to dictate the terms of the negotiation; that's what it does. There is only one way to describe this deal: it is Jeremy Corbyn's surrender bill.

"It means running up the white flag...I want to make clear to everybody in this House there are no circumstances in which I will ever accept anything like it.

"I will never surrender the control of our negotiations in the way the Leader of the Opposition is demanding," declared Mr Johnson.

The Labour leader urged MPs to stop the PM from "riding roughshod" over the constitution so that a "cabal" in Downing Street could "crash us out without a deal".

"He isn't winning friends in Europe, he's losing friends at home,” insisted Mr Corbyn, adding: “His is a government with no mandate, no morals and, as of today, no majority."

The SNP’s Ian Blackford denounced the Government as “shambolic” and said the PM’s decision to suspend Parliament for five weeks was “robbing the people of power…In true Trumpian style, the PM is acting more like a tin-pot dictator than a democrat.”

Tory grandee Ken Clarke accused the PM of plotting to fight a hasty election before voters realised the true consequences of a no-deal Brexit.

The Europhile former Chancellor said Mr Johnson’s "obvious strategy" was to “set conditions which make no-deal inevitable, to make sure as much blame as possible is attached to the EU and to this House for that consequence and then as quickly as he can fight a flag-waving general election before the consequences of no-deal become too obvious to the public".

But the PM hit back. Stressing how he was a lifelong admirer of Mr Clarke, he strongly denied that he wanted an election but, rather, “to get the deal done".

Earlier, the extent of the damage the civil war was doing to the Tory brand was on full display.

Justine Greening, the former Education Secretary, made clear she would rebel and announced she would not stand for the party at the next General Election.

The London MP said her concerns that the Tory Party was morphing into Nigel Farage's Brexit Party had "come to pass" and Mr Johnson was now offering the country a "lose-lose" situation by threatening a general election in which the choice would be between a no-deal Brexit and a Corbyn government.

Dominic Grieve, the former Attorney General, said the PM was displaying a “new ruthlessness,” accusing him of putting the Tory Party on a potential path to destruction.

Insisting he was a true Conservative, the Buckinghamshire MP nonetheless said if “ultimately, the Prime Minister and leader of my party is doing something which is so fundamentally wrong, then I can't continue supporting it”.

But the strongest attack came from Philip Hammond, the former Chancellor, who condemned the “aggressive operation” from Whitehall against certain Conservative MPs, including himself, and decried the “entryists,” who were trying to turn the party “from a broad church to narrow faction”. This was believed to be a reference to Dominic Cummings, the former Leave campaign chief, who is now Mr Johnson’s de facto chief of staff.

After being endorsed by his Surrey constituency as their next election candidate, Mr Hammond warned Tory HQ that it would be the “fight of a lifetime” if it tried to remove the party whip from him.

A Downing St source responded to the former Chancellor’s remarks by describing them as an “hysterical meltdown".