Home secretary likely to make final two and face members’ vote as Andrea Leadsom’s bid builds enough momentum to overtake Gove’s campaign

Support for Theresa May is surging among Conservative MPs, with almost 100 now backing her bid to become party leader as Michael Gove’s late entry into the race struggled to gain momentum.

The growing number of endorsements for the home secretary are likely to guarantee that she will make the final two and face a vote of grassroots members. Gove, however, has been failing to win over significant numbers of backers of Boris Johnson, who withdrew from the race on Thursday.

May has attracted the support of a number of cabinet members, including Amber Rudd, Justine Greening, Jeremy Hunt, Michael Fallon and Patrick McLoughlin.

Thérèse Coffey MP also said she was supporting May, because “she is a strong, credible leader who has delivered on many things and can be trusted to step into the prime minister’s shoes and enter into the negotiations in Europe”.

At his launch event, Gove was unapologetic about abandoning his Vote Leave ally Johnson at the 11th hour, despite fury from some Conservative colleagues who accused him of treachery. He said he had come to the conclusion that he simply could not recommend the former London mayor to friends or colleagues.

“I never thought I’d ever be in this position. I did not want it, indeed I did almost everything not to be a candidate for the leadership of this party,” Gove said in a speech in which he set out plans for radical reform to public services and to capitalism itself.

His allies admitted it had been a bumpy start, with only a handful of MPs turning up for his opening speech compared with dozens a day earlier in support of May. Gove is estimated to have the public support of 20 MPs.

Dominic Raab, who switched from supporting Johnson to Gove, said: “Michael was box office today. People saw the optimist, the visionary, the social reformer of his generation. It wasn’t an easy way to start, but when the dust settles we are deciding on who will lead our country to fulfil its true potential. He’s the candidate who can inspire and deliver.”

But Gove is likely to face a fierce contest from another Brexit-supporting MP. Andrea Leadsom, whose support was starting to rise on Friday, has received a boost by winning the support of former party leader, Iain Duncan Smith.

He said he had “huge confidence in her strength, her experience, her wide range of capabilities, her calm manner and her ability to achieve objectives even against considerable odds”. Leadsom’s growing support meant she leapfrogged Gove to become second favourite according to bookmakers.

Penny Mordaunt, an MP in Leadsom’s campaign team, said: “The phones are in meltdown. We are getting good support and the momentum is with us. You will see over the weekend there will be more names coming out.”

She said MPs saw Leadsom as someone with both “human qualities and the technical expertise”.

MP Anne Marie Morris said Leadsom was able to straddle both economic competence, after decades in the City and time as a Treasury and energy minister, and social justice, following work on the bonding between parents and babies.

Some MPs told the Guardian they were prepared to back Leadsom – who will launch her campaign on Monday with a promise to be a fresh candidate – simply to reduce Gove’s chances of making the final two. One said they felt Gove had behaved “incredibly” and warned that if he got anywhere near the top job, 51 Tory MPs would be ready to send in letters triggering a second challenge.

Others suggested that May supporters would be prepared to lend their support to Leadsom to boost her chances. “MPs are all playing for numbers, and you have to live with it in politics. It is about who is best at playing the game.”

The contenders, who also include work and pensions secretary Stephen Crabb and eurosceptic former defence secretary Liam Fox, will take part in a hustings in parliament on Monday at 5.30pm before the first round of voting on Tuesday. That will decide who is first to be knocked out of the race with follow-up votes on Thursday, and if necessary, the week after until it is down to a final two.

Ben Wallace, an MP who was working on Johnson’s campaign, wrote on Twitter that Gove would be like Theon Greyjoy from TV series Game of Thrones, “by the time I am finished with him”. The character was tortured in a dungeon and had his penis removed.

The reason for Gove’s decision to pull his support from Johnson, effectively ending his colleague’s candidacy, was the subject of rumours across Westminster.

Some claimed the justice secretary was angry that Johnson had failed to tie up the support of Leadsom after failing to give her a note that promised she would be in the top three positions of his future team. Some also said Gove was upset that he was not being offered the role of chancellor.

Facebook Twitter Pinterest Former Conservative leader Iain Duncan Smith lent his support to fellow leave campaigner Andrea Leadsom. Photograph: Rob Stothard/Getty Images

But others disputed that version, saying Johnson had promised Gove the Treasury job last weekend. They also insisted that he had given a written message to Nick Boles to pass on, pointing out that he was among the MPs who also swung behind Gove’s bid.

Gove said he had been unsure because of his own character weaknesses. “I was so very reluctant because I know my limitations. Whatever charisma is, I don’t have it; whatever glamour may be, I don’t think anyone could ever associate me with it. But – at every step in my political life – I’ve asked myself one question: what is the right thing to do? What does your heart tell you?”

Gove said it had been a wrench to battle against Cameron in the EU referendum, because he was a friend whose “leadership qualities I so much admire”. But the fight for Brexit was a “matter of deep principle”.

In a 5,000-word, policy-packed speech – which Gove said he had only started writing the day before, the former education secretary argued that the country should be governed by a politician who had campaigned to leave the EU, and that he had originally thought Johnson was the man to lead that effort. He promised to spend £100m more a week on the NHS by 2020.

“I wanted that plan to work,” he said. “I worked night and day for it. But I came to realise this week that, for all Boris’s formidable talents, he was not the right person for the task.

“That realisation meant that I once more faced a difficult decision. Could I recommend to friends, colleagues and the country a course in which I no longer believed?” He said the answer was no, which was why he decided to run.

In a final plea to his electorate, Gove said his bid was not a result of calculation but a “burning desire” to transform the country. “I know I have the experience, the energy and, perhaps most importantly, the sense of urgency,” Gove said. “Because away from Westminster there is a country where far too many people are denied the chance to write their own life story, to use their God-given talents and be the best they can be.”

He said it had been an “extraordinary, testing, momentous time for Britain” but he wanted to make it through “stronger and prouder”.

Gove spoke about making changes to education and prison policy and to capitalism itself, although without the details yet set out in many areas. Asked if Johnson would have a place in his cabinet, Gove said he would wait to be elected before handing out jobs.