Liz Truss could boost the Conservative party's ratings if she becomes the next Prime Minister, according to Labour.
Internal analysis circulated within Mr Starmer’s party claimed the Foreign Secretary would boost the Conservatives poll ratings.
The leaked document claims the Foreign Secretary would improve the Tories position, but only for a short while as it would be short lived as “untrustworthiness, inauthenticity and a lack of grip” would stop voters liking her.
Since the Tory leadership race kicked off last month, candidates have been shouting over each other in a bid to claim they are the hopeful that the Labour party would "fear the most".
The analysis comes as Labour held their biggest poll lead over the Tories for more than 10 years.
The YouGov poll showed Labour had the backing of 43 per cent of voters, followed by the Conservatives with just 28 per cent.
Rishi Sunak accused Ms Truss of “promising the earth to everybody” in a bid to become the next PM.
The former chancellor also fuelled speculation that he may decline to serve in any Truss administration if defeated, as he suggested that ministers need to agree with a prime minister on the “big things”.
Research showed Mr Starmer is more trusted by the public than either of the Tory leadership candidates, research has revealed.
A poll by Ipsos UK found more Brits have faith in the Labour leader to tell the truth than Rishi Sunak, Liz Truss - or ousted PM Boris Johnson.
Some 61% of people polled said they thought Mr Johnson told the truth “not very often” or “never” - almost double the number who thought the same about Mr Starmer.
About 23% of people said they believed Mr Sunak told the truth all or most of the time, just ahead of Liz Truss with 22%.
Even among people who voted for him, only 29% trust him.
Three in 10 trust their own representative, but this falls to less than two in 10 (19%) when asked about MPs in general.
And just 18% trust Government ministers to tell the truth.
But the pollster said it did not necessarily mean “smooth sailing” for the Labour leader.
