Rishi Sunak wants to try to sign up more than half of Tory MPs in the next few days as part of his campaign to persuade party members to back him.
The former chancellor received more votes in the final leadership ballot of MPs than any of his rivals – but his level of support represented just 38 per cent of the parliamentary party.
The Telegraph understands Mr Sunak’s team hopes that, by attracting as many backers as possible from those who previously supported third-placed Penny Mordaunt, he could get his tally above 50 per cent and show members he is the only candidate able to unite the party in the Commons.
Mr Sunak’s victory in the last ballot was narrow, with his 137 votes representing 38 per cent of Tory MPs. Liz Truss’s 113 votes represented 32 per cent.
His opponents have pointed out that this compares poorly with Boris Johnson’s 66 per cent of MPs’ votes in the final round in 2019.
It comes as Lord Howard of Lympne, the former Tory leader, became the latest high-profile figure to endorse Mr Sunak, saying his policies were more Thatcherite than those of Ms Truss.
Writing for The Telegraph, Lord Howard said: “Because debt is so high, it would be foolish for us to embark on a tax-cutting spree which would lead to even higher debt and feed the monster of inflation that we absolutely must tame.
“That is why Rishi is absolutely right to insist that we must bring down inflation first and steer our economy to a place where it would be safe to cut taxes.
“I was privileged to serve in Margaret Thatcher’s cabinet. She certainly did not believe in cutting taxes in an irresponsible way. Nor does Rishi, and he is absolutely right.”
He said Mr Sunak could emulate the achievement of Harold Macmillan, who won an election two years after the Tory party was at a low ebb in the wake of the Suez crisis.
Speaking to The Times, Mr Sunak said he will be putting the country on a “crisis footing” from day one if he becomes the next Conservative leader.
He said inflation was the “number one challenge” and he was worried about it becoming “entrenched”.
He added: “Anyone who doesn’t take really seriously the fact that inflation is running at the level it is is being hugely complacent.”
The former chancellor said he supports the Rwanda immigration policy, adding: “We need to make sure it works properly.”
Tory MP Richard Holden, a Sunak supporter, said: “It’s now time for MPs to get behind Rishi, because the polls show he is the best candidate to beat Labour in the north of England, the Liberal Democrats in the south of England, and the SNP in Scotland.”
A key ally of Ms Mordaunt has thrown his weight behind Mr Sunak amid claims that her supporters are organising a “Stop Liz Truss” campaign.
George Freeman, a former science minister, said he backed the former chancellor because he was the only one who supported “innovation”.
He added: “We face a post-pandemic global economic crisis of inflation. The only way to unlock non-inflationary growth and prosperity is through innovation. We need a prime minister who gets science, technology, innovation. For me, it’s Rishi Sunak.”
In an article for The Times, he wrote: “We need someone that will tackle the economy in a responsible way, with a proven track record of getting our country through an economic crisis. That is Rishi Sunak.”
Earlier this week, Mr Freeman blamed a “vicious” smear campaign for Ms Mordaunt’s failure to reach the last two. Her team deny claims her supporters are now orchestrating a campaign to stop Ms Truss.
The i newspaper reported that moderate Tory MPs are plotting to return to their constituencies to lobby their members to back Mr Sunak as leader amid concerns that Ms Truss could lose them their seats at the next election.
MPs and local party chairmen said they had been inundated with emails from members furious that Ms Mordaunt failed to make the final two.
“I’ve had members tear up their party membership over the result,” said one backbencher. “They are absolutely fuming. Several of us will now urge our members to vote for Rishi. That’s not because we support him, but because he is the better option than Liz.”
Another Mordaunt campaigner said: “It’s now about getting the best of a bad final two and, while he’s not what the grassroots want, Sunak at least has a chance of winning the next election. Under Truss, we’re just totally f-----.”