David Cameron has privately told sacked Tory rebels he will campaign for them in their constituencies if Boris Johnson forces them to stand at the next Election as independents, this newspaper can reveal.

The incendiary promise – which would see a former Prime Minister actively working against his own party – comes amid a furious backlash over the publication of Mr Cameron's explosive memoirs.

Mr Cameron broke his three-year silence to speak of his regret about Brexit and to savage former colleagues Mr Johnson and Michael Gove.

David Cameron (pictured) has privately told sacked Tory rebels he will campaign for them in their constituencies if Boris Johnson forces them to stand at the next Election as independents

Despite Mr Johnson's orders not to attack Mr Cameron, one Cabinet Minister last night told The Mail on Sunday that the former PM was 'bitter', while another questioned the logic of his Brexit remarks.

They said: 'I don't understand why he has done it. He will always be hated by Remainers and, by apologising for Brexit, he will never get credit for having being the person who enabled it.'

The Mail on Sunday can reveal that Mr Cameron has personally assured some of the 21 former Tory MPs kicked out after voting against the new Prime Minister that he would help them try to keep their seats in the Commons, even if it means pounding the streets of their constituencies with them against a Tory candidate.

The incendiary promise – which would see a former Prime Minister actively working against his own party – comes amid a furious backlash over the publication of Mr Cameron's explosive memoirs (pictured)

Mr Johnson has faced growing calls from within his own Cabinet and on the Tory benches to reinstate the rebels, including former Ministers Ken Clarke, Philip Hammond and Greg Clark.

A rebel source said: 'David reached out to lots of us and even said he would come and campaign if we stood as independents. He was very open about it on the phone.'

The revelation risks further souring relations between Mr Cameron and Mr Johnson, after Downing Street ordered Ministers not to attack the former PM in a bid to 'rise above' the memoirs row.

Despite insisting that he wanted the Prime Minister to succeed, Mr Cameron said Mr Johnson had behave 'appallingly' during the Brexit vote, and claimed his rival 'had left the truth at home' on the campaign.

Mr Cameron also criticised the decision to prorogue Parliament for five weeks and withdraw the whip from 21 Tories.

'Taking the whip from hard-working Conservative MPs and sharp practices using prorogation of Parliament have rebounded. I didn't support either. Neither do I think a No-Deal Brexit is a good idea,' he claimed.

Mr Cameron provoked anger after claiming the referendum 'had turned into this terrible Tory psychodrama and I couldn't seem to get through'.

Brexiteer and former Cabinet Minister Peter Lilley savaged the claim, saying that the 17.4 million people who voted for Brexit did not 'care a fig about Tory psychodramas or anything else'.

Mr Johnson has faced growing calls from within his own Cabinet and on the Tory benches to reinstate the rebels, including former Ministers Ken Clarke (left), Philip Hammond (right) and Greg Clark

The Tory peer told the BBC that Leave voters had 'put aside party loyalties and voted on the issue'.

And hitting back at claims that Mr Cameron regretted the referendum result, Lord Lilley added the former PM had once said, 'When the British people speak, their voice will be respected, not ignored' but 'now he's saying different things'.

Mr Cameron also faced anger from supporters of Mr Gove.

The pair fell out over Brexit, with Mr Cameron holding no punches in his memoirs about his troubled relationship with Mr Gove.

He chronicles in detail his decision to sack him as Education Secretary in 2014. However, a Whitehall veteran from the Cameron era hit out: 'If it were not for Mr Gove's education reforms, you could make the case that Mr Cameron's legacy in government was pretty thin.'

Mr Cameron was also criticised after writing about how he was almost expelled from Eton after being caught smoking cannabis, and admitted to getting 'off his head' on drug and smoking it with wife Samantha. Campaigners accused him of 'normalising' drug use.

'Mr Cameron should know better,' said Lucy Dawe, of the charity Cannabis Skunk Sense.

'Putting cannabis use in the same category as having a glass of wine in the evening is highly irresponsible.'