Liz Truss stressed her Conservative credentials and Cabinet experience as the Tory leadership contest became increasingly bitter, with voting beginning in the second ballot of MPs.
The Foreign Secretary is bidding to see off rival Penny Mordaunt, who is under fire from allies of Ms Truss after a surge of support for the trade minister.
Ms Mordaunt came second in the first round of voting on Wednesday, pushing Ms Truss into third place.
Former chancellor Rishi Sunak claimed the top spot but the battle to reach the final stage of the contest – in which the two candidates chosen by MPs face a vote by the party’s members – is far from over.
Ms Mordaunt’s strong performance saw her claim 67 votes, 17 more than Ms Truss, with Mr Sunak picking up the support of 88 MPs.
All eyes will be on Thursday’s ballot after the exit of former health secretary Jeremy Hunt and Chancellor Nadhim Zahawi, as the remaining candidates jostle for votes from party colleagues.
Strong opinion polling also buoyed Ms Mordaunt’s campaign, pushing her into the status of bookmakers’ favourite to become the next Tory leader and prime minister.
But supporters of Ms Truss seized on a scathing attack on Ms Mordaunt from former Brexit minister Lord Frost.
He told TalkTV: “I am quite surprised at where she is in this leadership race. She was my deputy – notionally, more than really – in the Brexit talks last year.
“I felt she did not master the detail that was necessary in the negotiations last year. She wouldn’t always deliver tough messages to the European Union when that was necessary.
“She wasn’t fully accountable, she wasn’t always visible. Sometimes I didn’t even know where she was. This became such a problem that, after six months, I had to ask the Prime Minister to move her on and find somebody else to support me.”
The remarks were seized on by the Truss campaign, with Treasury Chief Secretary Simon Clarke saying: “Lord Frost’s warning is a really serious one. Conservatives – and far more importantly our country – need a leader who is tested and ready.”
Ms Truss herself refused to be drawn into a war of words with the Mordaunt camp, telling her campaign launch: “The Conservative race shows what a broad range of talents we have in the Conservative Party. And we didn’t get there through identity politics.”
The Foreign Secretary also faced tough questions about whether her backing from Johnson loyalists could prove fatal to her ambitions to succeed him as Prime Minister.
“I am a loyal person. I am loyal to Boris Johnson. I supported our Prime Minister’s aspirations and I want to deliver the promise of the 2019 manifesto,” she said on Thursday morning, to cheers from her campaign team.
Allies of Penny Mordaunt said she had “nothing but respect” for Lord Frost despite his scathing attack on her.
A source in the Penny Mordaunt campaign said: “Penny has nothing but respect for Lord Frost.
“He did a huge amount to assist our negotiations until he resigned from Government.
“Penny will always fight for Brexit and always has.”
A second round of voting will see the lowest placed of the six remaining candidates eliminated from the race – although pressure is already growing from Ms Truss’s allies for Suella Braverman and Kemi Badenoch to abandon their bids and for their supporters on the right of the party to unite around the Foreign Secretary.
Ms Braverman scraped into the second round with 32 votes – candidates with fewer than 30 were eliminated – while Ms Badenoch had 40.
Work and Pensions Secretary Therese Coffey, a key player in the Truss campaign, told Sky News: “The reason why I think that supporters of Suella and Kemi should come and join Liz is because a lot of their policies are in a very similar direction – about having a free economy, about making sure we stand up for the United Kingdom and be proud of our country.”
But even as MPs voted, Ms Braverman was adamant she would not be quitting.
Her campaign team believes that getting her into the debates, due to begin on Friday night, is key to her chances.
The Attorney General said: “We are in this to win it.”
She said her plan to leave the European Convention on Human Rights and be “fearless in the fight for common sense vales” were popular with voters.
Meanwhile, Mr Sunak insisted his wealth and background in international finance does not bar him from understanding the plight of hard-pressed households.
He told BBC Radio 4’s Today programme: “I don’t judge people by their bank accounts, I judge them by their character, and I think people can judge me by my actions over the past couple of years.
“Whenever I have needed to step in to support people I have, and furlough is a fantastic example of that.
“But what I would say, as a Conservative, is I believe in hard work and aspiration and that’s my story, and if I’m prime minister then I’ll be making the case for that with vigour.”
He defended his economic plan, which would not involve the immediate tax cuts promised by his rivals.
“I think our number one economic priority is to tackle inflation and not make it worse,” he told Today.
“I will get taxes down in this Parliament, but I’m going to do so responsibly.
“Because I don’t cut taxes to win elections, I win elections to cut taxes, and I’m convinced that I’m the best person to beat Keir Starmer and the Labour Party at the next election.”
Rival camps have accused Mr Sunak’s operation of “dirty tricks” and “shenanigans” during the parliamentary election process, with the finger of blame pointed at former chief whip Sir Gavin Williamson.
Asked what Sir Gavin’s role is, Mr Sunak said: “Like all the Members of Parliament who are on my team, they are talking to colleagues and making the case for my candidacy because they believe that I am the best person to beat Keir Starmer and the Labour Party and I’m really grateful for all their support.”
In other developments:
– Ms Mordaunt used a piece in the Daily Mail to stress her credentials on defence, calling it the “first duty” of Government to honour the UK’s Nato commitment of spending 2.5% of GDP on defence by 2030.
– Ms Badenoch used a Times interview to describe herself as an “instinctive” tax-cutter but warned against “reckless” measures, while also suggesting the Bank of England should have come under greater scrutiny for not raising interest rates sooner.
– Tom Tugendhat said he has been “untainted by the last two years” of Mr Johnson’s Government, having not held ministerial office, and is “still in this fight”.
Under the Tory leadership rules, any candidate who does not get 30 votes or who finishes last in a round of voting is eliminated from the contest.
Tory MPs will continue to vote in subsequent rounds until two candidates are left, who will then battle it out over the summer to win the support of Conservative members, with their choice of the next prime minister being unveiled on September 5.
Mr Johnson will formally tender his resignation to the Queen to make way for his successor the following day, his official spokesman confirmed.
