Boris Johnson has intensified the battle over who will become the next Conservative prime minister by throwing his weight behind Andrea Leadsom, who he said offered “the zap, the drive, and the determination” that is needed to lead the country.
The decision by the former London mayor to support the energy minister’s campaign is likely to result in more MPs lining up behind Leadsom, who is now the clear second favourite after the home secretary, Theresa May.
“She has long championed the needs of the most vulnerable in our society. She has a better understanding of finance than almost anyone else in parliament. She has considerable experience of government. She is level-headed, kind, trustworthy, approachable and the possessor of a good sense of humour,” said Johnson, who argued that she had specialised in the “EU question”.
The MP – whose own leadership campaign collapsed last week after the justice secretary Michael Gove abandoned him at the 11th hour – said her role in the Vote Leave campaign made her well-placed to “help forge a great post-Brexit future for Britain and Europe”. He added that, most importantly, she could bring together the leave and remain camps.
The support of Johnson will be seen as a coup for Leadsom, as he is a popular figure among the grassroots and has earned considerable sympathy since his own campaign was thwarted. The manner in which Gove withdrew his support in order to enter the race himself has angered some colleagues and prevented the justice secretary from gaining momentum.
Leadsom could now see her support among MPs hugely boosted by Johnson’s decision, as there are a number of Tory politicians who were going to back him but have not yet said who they will choose instead.
If they swing behind Leadsom, the battle will become a clear two-horse race, with the politicians virtually neck and neck among the grassroots, according to a ConservativeHome poll. It has the energy minister on 38% and the home secretary on 37%, with the other candidates falling way behind.
One MP reacted to the news by declaring that it was “revenge served cold” after Johnson’s own humiliation at the hands of Gove. The Tory politician suggested that Leadsom could now get up to 25 additional MPs backing her bid, a move that would inflict serious damage on the campaigns of Gove, Stephen Crabb and Liam Fox.
Earlier, May – who has secured the support of 100 MPs including 10 cabinet members – was forced on to the defensive over whether EU citizens would be able to remain in the UK, after Leadsom guaranteed the rights of more than 3m migrants during a speech to launch her campaign. “We must give them certainty; they will not be bargaining chips in our negotiations,” she said.
Crabb and Gove have given similar assurances, as both sought to differentiate themselves from May.
The home secretary responded at the start of a private Tory party hustings in parliament on Monday night by saying that the issue would be dealt with in Brexit negotiations. She said she wanted to provide guarantees, but talks would also have to focus on protecting the rights of millions of British people living abroad.
May told her party’s MPs that she wanted to take the issue head-on after a controversial session in parliament in which the immigration minister, James Brokenshire, faced criticism from Labour MPs and his party’s own benches as he laid out the government position.
Leadsom was unclear on exactly how arrangements might work for those arriving in Britain after 23 June, the date when the country voted to leave the European Union. “On free movement, we have to very quickly get in control of the numbers of people who are coming here, whether that means we have to have a transitional arrangement since the referendum, or indeed since negotiations start,” she said.
“But it is very clear that what we must prioritise as soon as possible, now there is clarity about the direction that we are going in, is that we want to control the numbers of people coming here.”
The issue has caused some concern among May supporters, such as the MP Sarah Wollaston, who called in parliament for security for “some 55,000 members of our NHS workforce” who qualified elsewhere in the European Union, and 80,000 members of the care sector.
But Wollaston told the Guardian that May had persuaded MPs that her position was the most sensible. “It beggars belief that those who were part of a campaign that cynically manipulated immigration in the closing weeks of the referendum campaign are now accusing the home secretary of using EU citizens resident in the UK as ‘bargaining chips’.
“Theresa May is absolutely clear that she recognises the contribution that EU citizens make to this country and that she wants them to be able to stay, but is the most honest of all the leadership candidates in also speaking up equally for the rights of British citizens who would like to remain resident in other EU nations.”
The energy secretary, Amber Rudd, said May had been “without question the most statesmanlike in performance and in answering questions”.
At the meeting, Leadsom came under pressure over the support given to her campaign by Leave.EU, the campaign group founded by Ukip donor Arron Banks. David Morris, an MP supporting Crabb, said he had received an email that appeared to be from someone outside the Conservatives asking him to support her campaign.
However, she dismissed the idea that her campaign was being infiltrated by Ukip supporters. One MP supporting Leadsom said: “She distanced herself from Nigel Farage and made it clear she wouldn’t accept any funding from Arron Banks or anyone like that.”
Some MPs supporting other camps accused Leadsom of losing the room by focusing heavily on the attachment theory of babies – an issue she is passionate about and has set up charities to focus on. One said that the minister had talked a lot about her “three b’s – Brussels, banks and babies”.
Gove was not asked about his decision to abandon Johnson but was asked more than once whether Dominic Cummings, a key figure in the leave campaign who is controversial among MPs, would be part of his team. The justice secretary said no, joking that he would probably only see his former adviser for a drink while watching their football team, QPR.
Gove said he was not sure whether to expect the bar bill to be picked up by Ben Wallace, a Johnson supporter who has attacked the justice secretary for an “emotional need to gossip, particularly when drink is taken”. Wallace had previously written on Twitter suggesting that he would like to torture Gove in a way similar to that carried out on a Game of Thrones character.
Gove’s supporters emerged from the meeting to say that he had done a brilliant job focusing on policy, but his opponents said there had been “daggers” in the room from those who felt he betrayed his friend.
MP Chris Skidmore praised Crabb’s performance: “Stephen gave a polished performance, above all highlighting the need for unity and for an end to ‘remain’ and ‘leave’ tags. It felt as though just having a hustings like that was part of the healing process.”
Elsewhere, May has said she will back a parliamentary vote before parliament’s summer recess on renewing the Trident nuclear weapons programme.
“When it comes to the nuclear deterrent, the national interest is clear, the Conservatives are united, and we have waited long enough,” wrote May in an article in the Daily Mail, which has come out in support of her leadership bid. “The world has become a more dangerous place than it has been for many years, and a Conservative government I lead will make a strong defence an important priority.”