THERESA May is clinging onto power today after a minister openly questioned her Brexit policy and she was forced into an embarrassing U-turn on releasing a downbeat economic analysis about Britain’s EU withdrawal.

As the Conservative Party appears increasingly torn on whether to back her or sack her, the Tory-supporting magazine, The Spectator, challenged the Prime Minister to “lead or go”.

Meanwhile, it has been suggested a senior minister outside the Cabinet is preparing to resign and denounce the PM in a dramatic move that could cause further instability and even her downfall.

The respected Tory MP has, according to The Sun, told allies that he is close to resigning in a principled protest at Mrs May's failing premiership.

He then intends to issue a call from the backbenches for the party to take a new direction.

In recent days, siren voices against Mrs May have been growing louder as it is suggested the number of Conservative MPs calling for her to stand down is perilously close to the 48 needed to spark a leadership contest.

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Grant Shapps, the former party Chairman, has said that unless the PM announced a timetable to bring to a close her “uninspiring” leadership, then she could face a vote of no confidence.

Tory backbencher Heidi Allen has urged Mrs May to "get a grip" while her colleague Johnny Mercer suggested the “window is closing” on their leader being able to turn things around.

However, others have called for loyalty, pointing out that to replace the PM in the middle of intense Brexit negotiations would be “madness” while senior ministers like David Mundell, the Scottish Secretary, are urgently colleagues to “get behind Theresa”.

During her China trade trip, Mrs May defied her critics, declaring: “I'm not a quitter.”

However, the Government appeared to be the creator of its own misfortune after the leak of draft analysis suggested that growth would be lower whatever Brexit path was taken.

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In Beijing, the PM was adamant that the leak was a “selective interpretation of a very preliminary analysis,” which had not been signed off by ministers and did not cover the bespoke deal the Government was seeking.

Stressing how MPs would get a full analysis before the key “meaningful vote” on the final Brexit deal, she told reporters: “But it would be wrong to publish analysis before that analysis has been completed and it would also be wrong to publish analysis which might prejudice our negotiating position.”

However, after the Labour and SNP leaderships demanded full disclosure, the Opposition said it would force the matter to a binding Commons vote.

With the Government facing possible defeat, Robin Walker, the Brexit Minister, announced a climbdown and said it would provide the analysis to the Commons Brexit Committee and all MPs "on a strictly confidential basis”.

Commons Speaker John Bercow said the analysis should be made available "as a matter of urgency".

Sir Keir Starmer, the Shadow Brexit Secretary, said: "I look forward to studying the documents in full and helping to ensure that in future Brexit policy is driven by evidence, not ideology."

He added: "It's time the Prime Minister reflected on her reckless red lines that are clearly not in the national interest."

During the Opposition debate on the leaked report, Ken Clarke, the Europhile former Conservative Chancellor, accused the Government of adopting a "cult of secrecy" while his fellow Remainer Anna Soubry launched a scathing attack on her "hard Brexiteer" colleagues, warning that they would "destroy" the party and Mrs May to get the Brexit they wanted.

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The SNP’s Deirdre Brock likened the Government’s strategy to a “train in a spaghetti western running onto a half-collapsed bridge…We know the plunge is coming".

Earlier, Phillip Lee, the Justice Minister, was hauled over the coals by Julian Smith, the Chief Whip, after he tweeted that if the leaked figures were “anywhere near right”, then there should be a “serious question” about the Government’s Brexit policy.

“It’s time for evidence, not dogma, to show the way,” he declared.

Asked why Mr Lee had been disciplined when Steve Baker, the Brexit Minister, had not, even though he had enraged civil servants by suggesting their forecasts were “always wrong,” a Downing Street spokesman said: "It is the fact he aired it in public; that it was speculating about a leaked document in public."

During PMQs, Ian Blackford, the SNP leader at Westminster, again argued for Britain to stay in the single market to protect jobs and claimed the Tory civil war on Brexit had turned Mrs May’s Government into an “international embarrassment”.

Standing in for the PM, David Lidington, the Cabinet Office Minister - who today will travel to Scotland for talks with John Swinney, the Deputy First Minister, on amendments to the EU Withdrawal Bill – insisted his Cabinet colleague had set out a clear policy on Brexit in previous speeches and insisted the single market most valuable to Scotland was the UK single market, worth nearly £50 billion a year.

Later, Mr Blackford said the PM’s U-turn on the Brexit analysis showed “doing what you think is the ‘wrong’ thing now seems to be Government policy”.

Insisting Mrs May's leadership was "unravelling," the Highland MP added: “We have got a prime minister who is weak, who is not providing any leadership and is massively out of her depth.”