Senior Tories accused Boris Johnson of trying to torpedo Rishi Sunak’s bid to succeed him as prime minister – and of refusing to leave No 10 with good grace – as the leadership race descended into bitter infighting. As a trio of cabinet ministers entered the contest last night, senior MPs said the battle now risked inflicting even more damage on the party than the fall of Margaret Thatcher more than three decades ago. One party grandee accused Johnson of installing unsuitable MPs to middle-ranking and junior government posts when he knew he was on his way out “to cause maximum problems for his successor” who would inevitably have to sack most of them on taking office. “Those appointments were the most appalling thing I have seen in politics,” said the senior source. “It was obviously a move to sabotage his successor’s first weeks in office.” Another senior figure in the government added that Johnson was so incensed at the way he had been ousted, having won such a huge mandate at the 2019 general election, that he was now intent on exacting revenge on those he saw as responsible, and on influencing events wherever possible from the outside. “This is not an administration that is going to go quietly. There is a lot of anger about how this all happened,” said the source. “It is clear that much of it will now focus on Rishi. It is all very Trumpian.” A former vice-chairman of the 1922 committee of Conservative backbenchers, Sir Charles Walker, told the Observer that pleas for restraint were pointless because there was so much bad blood. “People like me can say until we are blue in the face that the Conservative party should not tear itself apart, but our pleas will fall on deaf ears. “Clearly the prime minister remains deeply bruised by the chancellor’s resignation. Rishi’s camp will have to soak up a lot of anger over the days to come. That will apply to whoever takes over.” Meanwhile, Johnson allies warned the party it would soon regret ditching him and accused the candidates vying to replace him of being incapable of repeating his successes. They say Sunak, in particular, faces questions of “loyalty and propriety” and accuse him of plotting his leadership bid for months while publicly professing his loyalty. On Saturday night , amid the succession turmoil, fresh allegations emerged that Johnson had lobbied for a job for a young woman who claims she was having a sexual relationship with him during his time as London mayor. According to the Sunday Times, the appointment was blocked because Kit Malthouse, then a senior figure in City Hall and now a cabinet minister, suggested the pair had an inappropriately close relationship. Johnson is said to have admitted pushing her forward for a job when the woman, who remains anonymous, confronted him in 2017. The claims follow reports last month that Johnson had tried to secure his wife, Carrie, a role as his chief of staff during his time as foreign secretary. The pair were having an affair at the time. He is also accused of helping an American businesswoman Jennifer Arcuri gain access to taxpayer-funded business trips after their affair in 2011. Foreign secretary Liz Truss, transport secretary Grant Shapps and the new chancellor, Nadhim Zahawi, all entered the leadership contest on Saturday night, alongside Sunak, the attorney general Suella Braverman, ex-minister Kemi Badenoch and the chair of the foreign affairs select committee, Tom Tugendhat. Shapps said he would focus on the cost of living crisis, while Zahawi promised to lower taxes “for individuals, families and business”. The chancellor also stressed his “culture war” credentials, saying he would “focus on letting children be children, protecting them from damaging and inappropriate nonsense being forced on them by radical activists”. Truss is expected to pledge to reverse the government’s recent national insurance rise when she officially launches her campaign this week. Others expected to declare in the coming days include former cabinet ministers Sajid Javid and Jeremy Hunt. Supporters of trade minister Penny Mordaunt are urging her to declare, while the defence secretary Ben Wallace – one of the bookies’ early favourites – said on Saturday that he would not be throwing his hat into the ring. The chair of the 1922 committee, Sir Graham Brady, will meet senior MP colleagues and members of the party’s board on Monday to decide how the contest will proceed. They are expected to agree a timetable that will see the number of candidates whittled down to two in a series of votes by MPs over the coming fortnight. Then there will be a programme of hustings for the final two, leading to a vote by party members, and the announcement of a new leader and prime minister in early September. According to the latest Opinium poll for the Observer, Sunak is the favourite among people who voted Conservative at the last general election. Some 55.4% said he would be a good prime minister. Javid was in second place on 50.5%. Those close to Johnson are struggling to decide which candidate they should back. “People are trying to work this out at the moment, the field is muddied by so many unrealistic candidates,” said one. “There is a strong concern in what you might call the pro-Boris camp of certain candidates – some, perfectly reasonably, have never bought into what Boris was trying to do. “Then there are those who have been running leadership campaigns from within the cabinet for some time, which is an act of the highest disloyalty. If you’re that far gone in terms of your support to the prime minister, you ought to have resigned months ago. I think that raises a fundamental question of loyalty and, indeed, of propriety.” Johnson loyalists will look at any potential campaign by the home secretary, Priti Patel, as well as Truss and Zahawi, before deciding who to back. Another Johnson supporter said “buyer’s remorse” was already beginning to grow among those who had helped to topple Johnson.