Andy Burnham’s popularity has plummeted by 20 points after coming into contact with voters, according to the latest YouGov poll.
The Mayor of Greater Manchester, who is running in next week’s Makerfield By-election, now sits at a net rating of minus 11 after previously peaking at plus nine in earlier polling.
Four in 10 Britons view him unfavourably compared to just three in 10 who hold a positive opinion.
The 20-point swing began in mid-May, shortly after the local elections sparked internal battles within the Labour Party.
Josh Simons vacated his Makerfield seat, creating a by-election opportunity for Mr Burnham to return to Westminster.
The YouGov study said: “In earlier polls in this series, Andy Burnham achieved a positive net favourability rating (+9 at its peak).
“However, his popularity declined starting from the middle of May – the period that encompassed the Labour party revolt against Keir Starmer that included Wes Streeting’s resignation and Josh Simons stepping down in Makerfield, triggering the by-election that Andy Burnham is likely to win.
“As a result, Burnham now takes a net favourability rating of -11 in our latest poll: 30 per cent of Britons like the would-be PM, versus 41 per cent who dislike him.”
Research from More in Common reveals that only 16 per cent of the public trust Mr Burnham to handle defence issues.
This is the same figure as Sir Keir’s rating.
Nearly half of respondents said they trusted neither leader, while a further fifth remained uncertain.
Just one in five believe the country could defend against an attack on home soil, with only around 12 per cent confident about overseas operations.
Roughly two-thirds doubt the UK could withstand either Russian or Chinese aggression.
In head-to-head polling, Ipsos reports that Mr Burnham holds a 13-point lead over Keir Starmer (25 per cent to 12 per cent) on who would make the better Prime Minister.
The data also show that 50 per cent of the public say “neither” or “no difference” when asked who would make a better leader.
Surveys of Labour Party members and 2024 voters consistently place Mr Burnham as the runaway favourite to take over the party if Mr Starmer stands down following a series of high-profile resignations.
Sir Keir Starmer has vowed to contest any upcoming leadership challenge, insisting that he will not walk away and that his decision to stay is driven by a “deep sense of duty”.
Wes Streeting resigned from his role as Health Secretary on May 14, saying he had lost confidence in the Prime Minister’s leadership.
Just last week, John Healey stepped down as Defence Secretary following a dispute with the Treasury over the Defence Investment Plan.
Over half of Britons (52 per cent) believe that the Government need to increase defence spending, including nearly two-thirds (63 per cent) of Labour voters.
The public is twice as likely to say that Defence Secretary John Healey was right (46 per cent) to resign than not (23 per cent), according to the More in Common research.
