Liz Truss ahead in polls amid hopes ballot delay could benefit Rishi Sunak

Sixty per cent of Conservative Party members polled by YouGov say they intend to vote for Truss

Liz Truss and Rishi Sunak in the BBC Conservative Party leadership debate in Stoke-on-Trent, England, on July 25. AP

A new poll shows Rishi Sunak has lost ground in the Tory leadership race but a ballot delivery delay over security concerns could give him more time to make an impression before votes are cast.

Foreign Secretary Liz Truss is well ahead of the former chancellor in a YouGov poll, with her lead increasing to 34 points.

The research was conducted between July 29 and August 2, and shows 60 per cent of party members polled say they intend to vote for Ms Truss, up from 49 per cent since July 20 to 21 when the two first made the final cut.

Support for Mr Sunak has dropped from 31 per cent to 26 per cent according to YouGov, while the rest of the 1,043 Conservative party members polled say they are undecided or will not vote.

In a further blow to him, YouGov data also showed 83 per cent of those who say they intend to vote for Ms Truss also say they have made up their minds.

Only 17 per cent say they might still change their mind while 29 per cent of Mr Sunak’s supporters say they might still vote differently.

UK Conservatives on the leadership campaign trail - in pictures

But the Sunak campaign will be hoping the extra time to make their case before the first votes are cast will be in their favour.

The Truss campaign spent Tuesday in damage control after abandoning a policy to slash £8.8 billion ($10.6bn) from public sector pay outside London.

The announcement on Monday night met fierce opposition from senior Conservatives who said that it would be “levelling down” the nation by leaving nurses, police officers and teachers worse off.

Conservative Tees Valley mayor Ben Houchen, who is backing Mr Sunak, said the pay policy had left him “speechless”, and suggested it would have cost the party the next general election if introduced.

Mr Houchen told BBC Radio 4 that the “horrifically bad” policy “could be Liz’s dementia tax moment”, in a comparison to Theresa May’s scrapped policy that was blamed for her poor electoral performance in 2017.

Everything you need to know about Liz Truss - video

Mr Sunak’s camp argued that the move was no mistake, saying Ms Truss had called for the move when she was chief secretary to the Treasury in 2018.

But Ms Truss insisted her policy had been “misrepresented”.

“I never had any intention of changing the terms and conditions of teachers and nurses," she told the BBC in Dorset.

“But what I want to be clear about is I will not be going ahead with the regional pay boards, that is no longer my policy.”

Former chief whip Mark Harper told Ms Truss to stop “blaming journalists – reporting what a press release says isn’t ‘wilful misrepresentation’.”

“So this U-turn has wiped out £8.8bn in savings. Where are these going to come from now?” Mr Harper asked.

“An economic policy that can’t be paid for isn’t very Conservative. Mrs Thatcher would be livid.”

Everything you need to know about Rishi Sunak - video

But after a mixed day, Ms Truss did receive a campaign boost with backing from the Daily Mail.

“Members are making up their mind and they are supporting Liz," a Truss campaign source said on the YouGov polling.

“Her bold and ambitious plan for the country and economy is uniting Conservatives right across our nation.

"But we are certainly not complacent, Liz is fighting for every vote, meeting as many members as possible.”