Pressure on Theresa May to quit as Prime Minister grew last night after it emerged that former Tory Cabinet Minister Andrew Mitchell said she had lost all authority and should go.

Mr Mitchell, a close personal and political ally of Brexit Secretary David Davis – the favourite to succeed Mrs May – told a secret Commons dinner that the party needed a new leader.

A Conservative MP present at the gathering on June 26 said: ‘Mr Mitchell effectively said she was dead in the water. He said she was weak, had lost her authority, couldn’t go on and we needed a new leader. Some of us were very surprised and disagreed with him.’

David Davis is a favourite to succeed Theresa May. Pictured: Mr Davis posing with two women wearing T-shirts with the slogan ‘DD for me’ across their bosoms in 2005

The disclosure came amid growing reports that allies of Mr Davis have urged him to challenge Mrs May.

A sense of panic in the Tory high command grew last night as:

A ‘kamikaze’ group of Right-wing Tory MPs said they are ready to risk handing power to Jeremy Corbyn. They believe ousting Mrs May will kill off moves to ‘reverse’ Brexit – and say the danger of a ‘brief dose of a Corbyn Government’ would ‘end in disaster’, and boost the Tories in the long term;

No 10 was forced to deny rumours that Mrs May, who suffers from Type 1 diabetes, is on the verge of resigning ‘on health grounds’;

There were reports that rebel Tory MPs are threatening to write to Mrs May urging her to resign ‘for the sake of the party’.

A ‘kamikaze’ group of Right-wing Tory MPs said they are ready to risk handing power to Jeremy Corbyn. They believe ousting Theresa May (pictured) will kill off moves to ‘reverse’ Brexit – and say the danger of a ‘brief dose of a Corbyn Government’ would ‘end in disaster’, and boost the Tories in the long term

Mr Mitchell, who was forced to resign as Chief Whip in 2012 after swearing at a Downing Street policeman in the ‘Plebgate’ scandal, did not mention Mr Davis in his comments at the ‘One Nation’ Commons dining club of Tory MPs, of which he is the secretary.

Nor is there any suggestion Mr Davis himself is plotting against Mrs May, who marks a year in No 10 on Thursday. Publicly, he has said it would be a ‘catastrophe’ if she stepped down, though he has not ruled out standing for the leadership if she quits.

However, well-placed sources say allies of Mr Davis are trying to gain support from Tory MPs to oust Mrs May, with a coup followed by his ‘coronation’ as her successor. They hope to persuade rivals such as ambitious Foreign Secretary Boris Johnson and ‘soft Brexit’ Chancellor Philip Hammond not to oppose him on the grounds of unity.

Davis cheerleaders say that would avoid a divisive Tory leadership contest which could trigger another General Election – and the possibility of victory for Mr Corbyn. Labour are currently six points ahead in the polls.

If Mr Davis were to become PM, Mr Mitchell would be expected to make a return to the Cabinet.

Brexit Secretary David Davis arriving for a Cabinet meeting at 10 Downing Street in January. Well-placed sources say allies of Mr Davis are trying to gain support from Tory MPs to oust Mrs May, with a coup followed by his ‘coronation’ as her successor

Many plotters say Mr Davis, who unlike Mrs May campaigned for Britain to leave the EU, would have a much better chance of getting a good Brexit deal from Brussels. They fear that if Mrs May clings to power, Brexit will be ‘watered down’ – or even reversed – as pro-Remain MPs and EU chiefs prey on her weakness.

One hardline Tory Brexiteer said: ‘We have been campaigning for decades to leave the EU and will not stand by as it is diluted or derailed by Remainers or by a lack of leadership.

‘If replacing Mrs May safeguards Brexit and risks Corbyn getting in to No 10, it’s not as bad as losing Brexit. A brief dose of a Left-wing Government is not the end of the world. In the 1970s it spawned our greatest PM, Margaret Thatcher.’

But the ‘kamikaze’ plot was condemned as ‘infantile’ last night by Tory MP Sir Nicholas Soames. He said: ‘It is grossly irresponsible talk by people who regard ideological purity as more important than the national interest.

‘Most Conservative MPs and party members are determined to rally behind Mrs May. Any Tory who thinks electing a proto-Marxist Government is better than losing a hard Brexit is barmy.’

Some pro-Brexit MPs say Mrs May’s lack of authority after the Election makes it more difficult for her to achieve the hard Brexit they want, if necessary by walking away with no deal. They say Thatcherite Mr Davis has no such issues.

Mr Mitchell, who was forced to resign as Chief Whip in 2012 after swearing at a Downing Street policeman in the ‘Plebgate’ scandal, did not mention Mr Davis in his comments at the ‘One Nation’ Commons dining club of Tory MPs, of which he is the secretary

Brexiteer MPs are alarmed by reports that suggest Britain could end up with a deal like Norway’s – leaving the European Union in name but staying in the single market and continuing to pay billions into EU coffers, though with little power to curb immigration and no say in decision-making.

The MPs say such a deal would make a mockery of last year’s referendum. Technically, Britain cannot reverse its decision to leave the EU in March 2019, although Brussels chiefs have indicated that if Britain had a change of heart they would co-operate.

Writing in today’s Mail on Sunday, Mr Davis’s former deputy Brexit Minister David Jones accused pro-EU Conservative MPs of hatching a ‘cunning plot to stymie Brexit’.

Mr Jones said their aim was to allow it to proceed but ‘on such ludicrously pro-Brussels terms, we might as well have stayed exactly where we were. We will have left but not left. Just like the Eagles’ Hotel California, we can check out but we can never leave.’

If such a move succeeded it would ‘shatter Tory credibility for decades to come… a prospect too nightmarish to contemplate.’

Asked if he had said Mrs May should stand down, Mr Mitchell told The Mail on Sunday last night he would not comment ‘on what I may or may not have said at a private dinner. A lot of private conversations are going on.’

Yesterday, Mrs May was teased over her leadership prospects at the G20 press conference in Hamburg. Asked if she would still be Prime Minister when Donald Trump made his planned visit to the UK, she said: ‘I am looking forward to welcoming him to the country.’

He's a political bruiser, and I got the bruise to prove it

PROFILE - BY SIMON WALTERS, POLITICAL EDITOR

I have had a few run-ins with politicians over the years. But none has ever actually hit me physically, except David Davis. I had written something that irked him and as he passed me by he gave me a ‘friendly’ cuff round the head. One of those friendly cuffs that nearly knocks you off your chair and leaves your ears ringing.

Ex SAS Reservist Davis, a Thatcherite and Brexiteer, revels in his image as a working-class bruiser with brains. If the Tories want to bury their ‘posh’ image, making him PM should do it. Raised in a council house by a single mother and educated at a tough South London grammar school, he makes Jeremy Corbyn, growing up in a Shropshire pile, look to the manor born.

Davis’s disdain for political correctness has not always served him well.

In his disastrous leadership battle with David Cameron in 2005, he crassly posed with two women wearing T-shirts with the slogan ‘DD for me’ across their bosoms. Likewise he recently texted ‘I’m not blind’ to a pal amid reports he playfully tried to kiss Diane Abbott.

Mind you, it’s tame by Trump standards. And he defies stereotype. He once bragged to me that in his 1960s schooldays he single-handedly faced down a gang of bullies who tormented a gay boy. I told him I didn’t believe him and would track down the gang leader. I did – and it was more or less true.

Critics maintain Davis is flawed. ‘He is vain and when things go wrong, he blows up and walks away,’ said a former aide.

As Shadow Home Secretary, he resigned his safe Tory seat to fight a by-election after losing a Commons vote. Davis called it principle; detractors called it attention-seeking. The scars of being abandoned by your father at birth, as Davis was, can run deep.

But since becoming Brexit Secretary, he has confounded those who said his fighting talk would be exposed as bluster, earning plaudits for his cool handling of negotiations.

By the time Britain quits the EU in 2019, Davis will have turned 70. If Theresa May quits before then, some say the Tories should pick a younger leader like Stephen Crabb or Priti Patel, both in their 40s. But Davis supporters say let him complete Brexit as PM and he will step down selflessly so a young tyro can fight the next Election in 2022.

They all say that.

'Reversers' must not be allowed to destroy my party with their treason

COMMENT - BY DAVID JONES, FORMER BREXIT MINISTER

Parliament exists to reflect and enact the will of the people – not to subvert it. But amid the heat of high summer, it looks very much as if a plot is under way at Westminster.

A plot to stymie the clear, unequivocal wish of the British people to leave the EU, as expressed in last year’s referendum.

And it is, I very much regret to say, a plot that may yet succeed if MPs who truly respect that referendum result allow this conspiracy to proceed.

It is also a plot that would cause immeasurable damage to the Conservative Party for a generation, if not for ever.

Now, this may come as a shock to some of my fellow Brexiteers.

They may, naively, think that as Theresa May has already invoked Article 50 – the legal trigger beginning the Brexit process – the leaving process is irreversible.

We either reach an acceptable deal by March 30, 2019, as I hope and expect, or we don’t.

Either way, we’re out – based on legally prescribed EU procedure – on a fixed date in just under two years’ time.

Game, set and match, as Wimbledon umpires say.

But fanatically pro-EU MPs, both Labour and misguided Tory ones, too, have hatched a cunning plot.

Yes, we will leave the EU at that appointed time but on such ludicrously pro-Brussels terms, that we might as well have stayed exactly where we were. Still in the single market, with all the free movement of people that entails? Tick.

Still locked inside the customs union and unable to take advantage of a host of new free-trade deals with the rest of the world? Tick.

Still subject partly or wholly to the jurisdiction of the European Court of Justice? Tick.

And perhaps, most damagingly, of all, still having to send billions of British taxpayers’ pounds to Brussels each year? Tick again.

In other words, we will have left, but not left.

Just like the Hotel California, as rock group Eagles put it: We can check out, but we can never leave.

Of course, this deceit on the British people won’t be done in an instant.

It will be done over the next 18 months, slowly and gradually.

We will be told that this vital interest means we must stay in the single market, or that this essential cause means the customs union must still apply.

But eventually, the Remainers in both the Commons and the House of Lords – or Referendum Reversers as they are now known – will have successfully pulled the wool over voters and defied the expressed wish of the nation.

Such a subversion of last year’s clear referendum result would shatter the credibility of my party for decades to come.

How could we ever promise to honour any Election pledge ever again? Who would believe us?

The consequence would be political chaos and, who knows, the sight of Jeremy Corbyn marching into Downing Street at the head of a hard-Left Labour government, with all its dire consequences for the country.

BUT even worse, by overturning the referendum result, we will have rendered the solemn expression of the nation’s wishes null and void. Meaningless.

At a stroke, we will have plunged a dagger into democracy’s heart.

Of course, such is the zeal of the Reversers for clinging to Brussels’ apron strings, that such a treason against the British people will be worth it. A price worth paying, in their terms.

As I said, some of my Brexiteer colleagues will find this scenario absurd. Utterly implausible.

But its very implausibility is what may bring it to pass unless right-minded MPs are alerted to the danger now.

It is a prospect too nightmarish to contemplate.

We must wake up now if we are to prevent it.

PS. Thinking of running against the DD, Boris? Then maybe it's time to smarten up your act

Even his critics concede Boris Johnson is a smart man... though that clearly only applies to his brain, not his looks.

While Theresa May is hailed for her style and David Davis is usually seen in a sharp suit, the Foreign Secretary has been pictured jogging at various times in baggy pink shorts, ridiculous beanie hat and shabby fleece. What would Lord Palmerston say?