ES News email The latest headlines in your inbox twice a day Monday - Friday plus breaking news updates Enter your email address Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid You already have an account. Please log in Register with your social account or click here to log in I would like to receive lunchtime headlines Monday - Friday plus breaking news alerts, by email Update newsletter preferences

Tory MPs believe No 10 have planted “decoy” letters demanding a confidence vote in Theresa May in a bid to wrongfoot the real plotters trying to unseat her.

Up to eight letters demanding a ballot on the Prime Minister’s future are said to have been sent in by loyal MPs posing as rebels.

The idea is to withdraw some of the decoys if a total of 48 confidence letters - the number needed to trigger a ballot - is reached, creating a delay and alerting the whips to the danger.

It emerged on a day of strained nerves at Westminster after some MPs claimed to have learned that the 48 letters had been sent in, prompting rumours of a coup. The speculation only ended when the chairman of the 1922 Committee, Sir Graham Brady, assured friends that he had no plans “today” to visit No 10 to deliver bad news.

Suspicions of the extraordinary ruse to file decoy letters were revealed by a minister who told the Standard: “We think this is their ‘canary in the coal mine’ that would alert the Chief Whip to an attack on the Prime Minister and stop it from being successful.

“The moment that 48 letters are sent in, the decoys will tell the whips.”

The plan relies on the secretive role of Sir Graham, the chief of the so-called Men in Grey Suits, who is responsible for receiving letters asking for a confidence vote.

Under Conservative Party rules, a ballot is triggered automatically if 15 per cent of Conservative MPs - currently 48 of the total - request it in writing.

Sir Graham refuses to discuss with No 10 how many letters are kept in the safe in his office in Portcullis House. Crucially, however, if the trigger point is reached, he is expected to seek out the authors of any long-standing letters to check they have not changed their minds. That could alert a No 10 loyalist to raise the alarm.

But rebel MPs are aware of the rumours and have devised a counter-plot in which they would deluge Sir Graham with a dozen letters at once to ensure a confidence vote could not be stopped.

“If colleagues want to trigger a ballot, we would not mess about sending one letter at a time,” said the MP. “You would see an avalanche of letters, enough to decide the matter even if a few people lose their nerve or back off at the behest of the whips.

“All the whips’ stooges could really achieve is to prevent an ‘accidental discharge’ of the pearl-handled revolver. They could not stop a determined coup.”

Weekend reports claimed Tory rebels might be just two letters short of the total, but nobody really knows for sure.

Right winger Andrew Bridgen, one of just five MPs known to have sent letters, said that if contacted by Sir Graham he would not change his mind unless the PM abandoned her Chequers blueprint. “Toppling the Prime Minister isn’t the only solution,” he told Today.

Speaking on Newsnight, former Home Secretary Amber Rudd said it would be a “total indulgence” for Conservative MPs to bring down their leader. “I think it’s a huge mistake,” she said. “It would be total indulgence to think of the Conservative Party having a leadership election in the middle of these incredibly difficult negotiations.”

Only five MPs have said they sent letters: James Duddridge, Philip Davies, Andrea Jenkyns, Mr Bridgen and Nadine Dorries, all hardline Brexiteers. A sixth put in a letter and later withdrew it.

Last autumn, former Tory chairman Grant Shapps collected around 30 names of MPs willing to push Mrs May over the edge. Recent dismay at the state of negotiations is said to have driven more MPs to write.