Keir Starmer‘s party, which was 29 point behind the Tories in the so-called “Blue Wall” seats at the 2019 election, is now 21 points ahead.
The 42 constituencies polled are southern seats traditionally won by the Tories, where the Liberal Democrats came second last time.
But with Liz Truss’s popularity plumbing historic depths after a calamitous budget, the Tories are now set to win just 28 per cent of the vote in their own heartlands, down 22 percentage points.
Labour is on course to win 41 per cent of the vote, up 20 per cent, while the Lib Dems are also close to drawing level with the Conservatives on 24 per cent.
The result would see the south turn red and yellow on the political map, in some places for the first time.
The prime minister’s unpopularity seems to be a major drag on Tory fortunes, with her rating in the Blue Wall already at -35 per cent, according to the survey by Redfield and Wilton Strategies.
52 per cent of those in the Blue Wall, including 49 per cent of those who voted Conservative in 2019, say they disapprove of Ms Truss’s performance, with just 17 per cent approving.
Respondents in the seats were asked about the governemnt’s policy performance in different areas, and said they approved of how it handled the coronavirus pandemic and defence.
But in other areas such as the economy, the NHS, housing, and the environment, views were strongly negative.
Seats polled as part of the exercise include Jeremy Hunt’s south west Surrey constituency, Dominic Raab’s seat of Esher and Walton, and Boris Johnson’s area of Uxbridge and South Ruislip.
Others include Guildford, Wimbledon, Woking, Mole Valley, Bournemouth East and South Cambridgeshire – as well as Lewes, Colchester, and Watford.
Labour have jumped to a lead in excess of 20 or even 30 points nationally following the prime minister’s first budget with her chancellor Kwasi Kwarteng.
The so-called “fiscal event”, which included billions in unfunded tax cuts, sent financial markets haywire, nearly causing pension fund defaults and sending the cost of government and mortgage debt soaring.