A senior Conservative MP has warned Boris Johnson he will not “survive very long” if he pursues a “crash-out” Brexit, because fellow Tories will bring him down.

Dominic Grieve, who supports Britain remaining in the EU, predicted “a large number” of his colleagues would turn on the new prime minister, even joining a vote of no confidence to block a no-deal exit.

“There are a large number of Conservative MPs who will object to that happening and who will do everything possible to prevent it happening. I think the numbers are quite substantial,” the former attorney general said.

Mr Grieve admitted the new prime minister – widely expected to be Mr Johnson – could call a general election to win the public’s backing a for a no deal, if thwarted in parliament.

But he warned the Tories would lose badly, saying: “That is likely to be catastrophic for the future of the Conservative Party.”

Mr Johnson entered the Tory leadership race vowing to deliver Brexit by 31 October “deal or no deal”, but has since appeared to waver on that commitment.

Biggest lies told by Boris Johnson Show all 5 1 /5 Biggest lies told by Boris Johnson Biggest lies told by Boris Johnson Made-up quote for The Times Johnson was sacked from The Times newspaper in the late 1980s after he fabricated a quote from his godfather, the historian Colin Lucas, for a front-page article about the discovery of Edward II’s Rose Palace. “The trouble was that somewhere in my copy I managed to attribute to Colin the view that Edward II and Piers Gaveston would have been cavorting together in the Rose Palace,” he claimed. Alas, Gaveston was executed 13 years before the palace was built. “It was very nasty,” Mr Johnson added, before attempting to downplay it as nothing more than a schoolboy blunder. PA Biggest lies told by Boris Johnson Sacked from cabinet over cheating lie Michael Howard gave Boris Johnson two new jobs after becoming leader of the Conservatives in 2003 – party vice-chairman and shadow arts minister. He was sacked from both positions in November 2004 after assuring Mr Howard that tabloid reports of his affair with Spectator columnist Petronella Wyatt were false and an “inverted pyramid of piffle”. When the story was found to be true, he refused to resign. PA Biggest lies told by Boris Johnson Broken promise to boss In 1999 Johnson was offered editorship of The Spectator by owner Conrad Black on the condition that he would not stand as an MP while in the post. In 2001 he stood - and was elected - MP for Henley, though Black did allow him to continue as editor despite calling "ineffably duplicitous" PA Biggest lies told by Boris Johnson Misrepresenting the people of Liverpool As editor of The Spectator, he was forced to apologise for an article in the magazine which blamed drunken Liverpool fans for the 1989 Hillsborough disaster and suggested that the people of the city were wallowing in their victim status. “Anyone, journalist or politician, should say sorry to the people of Liverpool – as I do – for misrepresenting what happened at Hillsborough,” he said. PA Biggest lies told by Boris Johnson ‘I didn’t say anything about Turkey’ Johnson claimed in January, that he did not mention Turkey during the EU referendum campaign. In fact, he co-signed a letter stating that “the only way to avoid having common borders with Turkey is to vote Leave and take back control”. The Vote Leave campaign also produced a poster reading: “Turkey (population 76 million) is joining the EU”

Underlining the confusion, some Tory MPs have emerged from meetings with the leadership favourite convinced he would willingly crash out of the EU – while others were reassured he would pursue an orderly departure.

Mr Grieve told BBC Radio 4: “If the new prime minister announces taking the country on a magical mystery tour towards a 31 October crash out, I don't think that prime minister is going to survive very long.”

However, he pointed out that a successful no-confidence motion – which Labour has threatened to bring within days of Theresa May’s replacement being in place – would not necessarily put Jeremy Corbyn in No 10.

“If an administration falls on a vote of no confidence, there is 14 days to set up a new one,” Mr Grieve explained, adding: “It doesn't have to be Jeremy Corbyn at the helm.

“It could be another Conservative prime minister. It could be anybody who is able to command a majority in the House of Commons.”

Mr Grieve said the threat of a no-confidence defeat “might concentrate minds wonderfully on the need to have an administration run by somebody who has a tenable policy”.

Both Philip Hammond, the chancellor, and Ken Clarke, a former chancellor, have suggested they would join a no-confidence vote to thwart crashing out of the EU.

Furthermore, 26 Tories backed outsider Rory Stewart, who is committed to avoiding a no deal – while two were so disgusted with the choice of surviving candidates, after Mr Stewart was knocked out, that they spoiled their ballot papers.

Some Labour figures believe Mr Corbyn will step back from a no-confidence vote next month, believing the chances of success are greater in the autumn, as the Halloween deadline looms.