Boris Johnson’s hoped-for triumphant march into Downing Street this week is set to be dampened by a carefully timed series of resignations by senior ministers, who will retreat to the backbenches with a vow to thwart any moves towards a no-deal Brexit.

The announcements by Philip Hammond and David Gauke that they will step down on Wednesday, immediately before Johnson is likely to head to Buckingham Palace, highlight the perilous political climate for Theresa May’s expected successor.

It comes amid predictions that the Conservatives’ already wafer-thin working Commons majority of three could entirely disappear by the time MPs return from their summer recess, with mooted defections to the Lib Dems coming on top of a predicted byelection defeat.

Barring a hugely unexpected twist, Johnson is expected to be announced on Tuesday as the victor over Jeremy Hunt in the vote of Conservative members, formally taking over the next day, after May holds a valedictory prime minister’s questions.

However, some of the gloss will be removed with the promised resignations of Hammond, the chancellor, and Gauke, the justice secretary, with predictions that other ministers and junior ministers opposed to no deal, such as the international development secretary, Rory Stewart, could follow. It is understood that the business secretary, Greg Clark, another key cabinet voice against no deal, has no plans to resign.

Hammond took some apparent glee in announcing his intention live on BBC One’s Andrew Marr Show on Sunday. Asked if he expected to be sacked if Johnson took power, he replied: “No, I’m sure I’m not going to be sacked, because I’m going to resign before we get to that point.”

Play Video 0:51 Philip Hammond says he will resign if Boris Johnson becomes PM – video

He added: “I understand that his conditions for serving in his government would include accepting a no-deal exit on 31 October, and that’s not something that I could ever sign up to.”

Hammond denied that he would be recast on the backbenches as a serial rebel, insisting his only aim would be to stop a Johnson government forcing through no-deal without the explicit consent of MPs, for example by proroguing parliament.

“This is a parliamentary democracy, and if the new prime minister can persuade parliament to vote for a no-deal exit, then I will have to accept that,” he said. “But we can’t have wheezes like suspending parliament or proroguing parliament in order to deny parliament its voice.”

Earlier, Gauke said he also could not serve under Johnson. “Given that I’ve been in the cabinet since Theresa May came to power, I think the appropriate thing is for me to resign,” he told the Sunday Times, saying he would depart on Wednesday.

He added: “If the test of loyalty to stay in the cabinet is a commitment to support no deal on 31 October – which, to be fair to him, Boris has consistently said – then that’s not something I’m prepared to sign up to.”

Timeline Boris Johnson - three decades of sackings and giving offence Show Hide

Fired by the Times after landing a job at the newspaper through his family connections. In an article about the discovery of Edward II’s Rose Palace, Johnson allegedly invented a quote from his godfather, the historian Colin Lucas. Discussed plans to have a tabloid journalist beaten up with his fellow Old Etonian Darius Guppy. Johnson said he would try to obtain personal details of the News of the World journalist Stuart Collier. Guppy talked of hiring a contact from south London to assault Collier. In a Telegraph column he predicted that when Tony Blair arrived in Congo “the tribal warriors” would “all break out in watermelon smiles”. He added that the Queen loved the Commonwealth “partly because it supplies her with regular cheering crowds of flag-waving piccaninnies”. It was written the year after he became an MP. Compared same-sex marriage to polygamy and bestiality in his debut book, Friends, Voters, Countrymen. “If gay marriage was OK – and I was uncertain on the issue – then I saw no reason in principle why a union should not be consecrated between three men, as well as two men, or indeed three men and a dog,” said Johnson. Four years before, Johnson described gay men as “tank-topped bumboys” in his Telegraph column. Condemned for publishing an article as editor of the Spectator in which Liverpool fans were blamed for the 1989 Hillsborough disaster. While the article says the event was “undeniably” a tragedy, it added: “That is no excuse for Liverpool’s failure to acknowledge, even to this day, the part played in the disaster by drunken fans at the back of the crowd who mindlessly tried to fight their way into the ground that Saturday afternoon.” It also claimed that people in Liverpool “wallow” in their “victim status”. Fired by the then Tory leader, Michael Howard, from positions as shadow arts minister and party vice-chairman for lying about his extramarital affair with Spectator columnist Petronella Wyatt. When it transpired that tabloid reports, which Johnson had dismissed as an “inverted pyramid of piffle”, were true, he had refused to resign. Suggested that a rise in the number of Malaysian women attending university was down to their desire to find a husband. Suggested the “part-Kenyan” US president Barack Obama had an “ancestral dislike” of the UK. Won “most offensive Erdoğan poem” competition, two months before he was appointed foreign secretary. The limerick, for which he was handed £1,000 by the Spectator, described the Turkish president having sex with a goat. Caught on camera reciting a colonial-era poem by Rudyard Kipling in front of local dignitaries while on an official trip to Myanmar. Johnson, who was accused of “incredible insensitivity”, had been inside the sacred Buddhist site the Shwedagon Pagoda when he began murmuring the first verse of Mandalay, a later verse of which includes the line: “Bloomin’ idol made o’ mud, wot they called the Great Gawd Budd”. Criticised for making incorrect statement that the jailed British-Iranian Nazanin Zaghari-Ratcliffe had been “teaching people journalism” rather than being on holiday in Iran. The then foreign secretary condemned her conviction for spying but his comments were later cited as proof by Iran that she was engaged in “propaganda against the regime”. Came under fire for describing Muslim women in burqas as looking like “bank robbers” and “letter boxes”. Making the comments in his Telegraph column, Johnson also called the garments “oppressive” but added that Britain should not follow other countries in banning them in public. Media firestorm ensued after a neighbour recorded a loud altercation at the home Johnson shared with his partner, Carrie Symonds. Johnson refused to answer questions about the circumstances of the tape, which featured screaming, shouting and banging. A picture of the couple posing happily subsequently appeared in the media, but Johnson repeatedly refused to say who had taken or released the photograph, or whether it was an old picture. The UK's Supreme court rules that the advice prime minister Boris Johnson gave to the Queen over proroguing parliament was "unlawful, void, and of no effect" as it rules that his decision to prorogue parliament was unlawful.

Both Hammond and Gauke, along with Clark and Stewart, were among ministers who defied government whips last week over a backbench motion that makes it harder for Johnson to suspend parliament.

Hammond admitted to Marr that he had been texting other Tory MPs ahead of that vote, and had talked to opposition members. The prospect of a such a potentially noisy and well-connected cabal of ex-ministers could prove a significant headache for Johnson.

This group could also include the defence minister, Tobias Ellwood. While he has declined to say whether he would serve under Johnson, Ellwood told Sky News on Sunday that he could not countenance no deal as a plan. “No deal is not a destination. If you run away from the EU and say, ‘Fine, we don’t want to have a deal’, you’ll still have to crawl back, moments later, to say, ‘How are our financial services going to operate? How are operations with police going to work? How are citizens’ rights going to work?’” he said.

Hammond and other ministers have declined to say whether they could back a no-confidence motion against a Johnson government, and it seems unlikely that Labour would table one until after the summer recess, which begins on Thursday.

However, by the time MPs return at the start of September, Johnson’s difficulties could have multiplied, with the Lib Dems tipped to take the Brecon and Radnorshire seat from the Tories in an early August byelection.

While senior Lib Dem sources have played down reports that up to six disgruntled remain-minded Conservatives could defect to the party, they say enough are considering the move to potentially remove the rest of Johnson’s working majority.

“At the moment we don’t know how many we’ll get over the line,” a source said. “A lot depends on Johnson’s first 48 hours in No 10. At the moment, he seems more focused on Conservatives who are tempted by the Brexit party. I’m not sure the remainers are really on his radar. By September we’ll know a lot more.”

While Johnson has pledged to leave the EU on the current deadline of 31 October, with or without a deal, he has talked up his chances of reaching a swift new withdrawal agreement with the EU, one that would dispense with the backstop insurance policy for the Irish border.

But Simon Coveney, Ireland’s deputy prime minister, dismissed such ideas as fantasy on Sunday. “If the approach of the new British prime minister is that they’re going to tear up the withdrawal agreement, I think we’re in trouble. I think we’re all in trouble, quite frankly,” he told the Marr show. “That’s like saying, ‘Either give me what I want or I’m going to burn the house down for everybody’.”

Gordon Brown has also joined the chorus of warnings about no-deal, saying future historians would view it as “an act of economic self-harm that runs wholly counter to the national interest”.

Writing in the Guardian, the former Labour prime minister said: “For what message do we send about what kind of Britain we now are if we reject last week’s European offer to ditch the cliff-edge, and boast instead that we will not pay the money we owe to the EU: the equivalent of declaring an economic war on our neighbours?”