LIZ Truss has extended her lead over Rishi Sunak in the Conservative leadership race to 34 points, with 60 per cent of party members now saying they will vote for the Foreign Secretary to succeed Boris Johnson as Prime Minister.

A YouGov poll for The Times and Times Radio found that, as ballot paper start to go out, almost nine in ten Tory members had made up their minds. Just twenty-six per cent said they would support Mr Sunak. The rest were undecided or said they would not vote.

The poll, carried out over the past five days, suggests a significant widening of the lead for Ms Truss. She drew cheers from Tory members on Monday when she told a party hustings that First Minister Nicola Sturgeon was an "attention seeker" who ought to be "ignored". However her comments drew anger from many in Scotland with some commentators saying her remarks would be a gift to the SNP.

The poll found widespread resentment among party members about the way Mr Johnson was ousted from No 10 and suggests he would easily beat both candidates if he were on the ballot paper.

Some 53 per cent of members think it was wrong that Conservative MPs and ministers forced Mr Johnson’s resignation by quitting, compared with 41 per cent who think they made the right decision.

It also showed that given a choice between Johnson, Sunak and Truss, 40 per cent of members would vote for the Prime Minister to continue in office, 28 per cent would support Truss and only 23 per cent would back Sunak.

The poll found too that Ms Truss is ahead of Mr Sunak among all age groups, across different parts of the country and among men and women. The only category where the former chancellor beats Ms Truss is among Tories who supported Remain in the 2016 EU referendum. Mr Sunak backed Leave, whereas Ms Truss campaigned for Remain.

It represents a significant boost for Ms Truss after a difficult two days for her campaign.

Yesterday she was forced to abandon a pledge to cut government spending by up to £8.8 billion after it emerged that it would lead to pay cuts for more than five million teachers, nurses and other public sector workers.

The campaign was also unnerved by a separate private poll suggesting that Ms Truss’s lead over Mr Sunak had narrowed to five points.

However, the new YouGov survey of more than 1,000 registered Tory members shows that, Ms Truss has extended her lead after a series of big endorsements.

The polling is also the most detailed look yet at the views of party members on the two candidates to become Prime Minister. It found that more than 50 per cent believed that whoever was elected to succeed Mr Johnson would lose the party its majority at the next election, which is due to be held no later than January 2025. Only 19 per cent of members thought mr Sunak could lead the Tories to victory. Thirty-nine per cent thought the same of Ms Truss.

The poll also found significant dissatisfaction with the fractious nature of the campaign. Fifteen per cent of members said they thought the contest had shown the party in a good light, compared with 45 per cent who said it showed the Tories in a bad light.

The poll found that on most of the main issues the country faces, members felt that Truss would do better than Sunak. On the cost of living crisis she was backed by 55 per cent to his 31 per cent, on cross-Channel migration by 63 per cent to 18 per cent and on the NHS by 47 per cent to 30 per cent. The remainder said that they did not know.

As ballots went out it emerged that further security had been added, with one-use codes required to vote online. The result is due on September 5.

The party's Scottish hustings will take place in Perth on 16 August. Nine MSPs support Ms Truss while eight MSPs and two MPs back Mr Sunak.

Last night it emerged that the Conservative Party had delayed sending out ballot papers to vote for the next leader after government cybersecurity experts warned that the process was vulnerable to hackers.

In an email to members, the party warned that ballots — which were due to be dispatched this week — could arrive as late as August 11. Members will also not be allowed to change a submitted vote, as had been the plan, following the advice from the National Cyber Security Centre.

The polling appears to vindicate Truss’s decision to stay in Johnson’s cabinet as other ministers resigned around her.

The survey of 1,043 Tory party members showed that 51 per cent believe Sunak was wrong to step down as chancellor, compared with 40 per cent who think he was justified.

Throughout the hustings and debates, Mr Sunak has repeatedly been forced onto the defensive over his decision to quit after the Chris Pincher scandal.

At Monday’s hustings in Exeter, he tried to win members over by explaining that his decision had been made after months of soul-searching over Mr Johnson’s position.

“I wanted to give him the benefit of the doubt as long as I could,” Mr Sunak said. “But it got to a point where the government found itself on the wrong side of yet another ethical divide that was hard for me to defend.

“I thought that both our party and our country deserved better.” Tory members appear to care little about some of the big weaknesses commonly associated with the two leadership campaigns. Seventy per cent of members do not think it matters that Truss campaigned to remain in the European Union in the 2016 referendum, and 83 per cent do not care that she was a Liberal Democrat in her youth.

Although members are not entirely convinced of the need for a leadership election, a separate YouGov poll has suggested that the decision to remove Johnson may be starting to improve the Conservatives’ standing with the wider electorate.

The Tories have narrowed the gap behind Labour to one point, according to the latest survey of voting intention. Sir Keir Starmer, the Labour leader, had had a comfortable lead of seven points, and the findings suggest a sharp turn away from Labour after the party struggled to agree a stance on the recent railway strikes.

YouGov warned, however, that the swing towards the Tories was within the margin of error and that the poll could be an anomaly. It said that a consistent narrowing in the polls would have to emerge over the coming weeks to establish that the Conservatives had in fact made a recovery after a torrid few months.