A new mega-poll of London has warned that Labour is now 'under siege' from all sides, amid a huge surge in support for the Green Party and Reform.
More in Common carried out a landmark 'MRP' poll of the capital, asking 2,646 adults how they plan on voting over a three-week period.
The findings will cause gloom in Downing Street, as it reveals Labour's support has collapsed by 15 points since the general election, while the Greens have surged by 10 points.
While Labour is still in the lead across the nine million-strong city, it is down to just 28% support.
The Green Party is now breathing down Labour's neck on 20%, and is on course to win the highest vote share for the first time in a London borough.
It finds that Zack Polanski's party is now the most popular party in Hackney, leading by three points, and is within two points of Labour in Islington, Lambeth and Lewisham.
The insurgent left-wing party is also projected to come second to Labour in 16 boroughs, and come within five points of the governing party in five of them.
Keir Starmer's last-minute campaigning efforts appear not to have won over crucial swing voters
This would put Mr Polanski's party within reach of controlling almost a third of the capital at the next set of London local elections if they continue gaining support at Labour's expense.
Reform UK has surged in outer London, and is projected to lead the vote in Havering by nine points.
In Bexley, the leafy south east suburb once represented in Parliament by Ted Heath, Reform is now neck-and-neck with the Conservatives.
Nigel Farage's party is also set to deal the Tories another bloody nose in Bromley, rising to 21.3% of the vote.
The right-wing party has also surged to 24% in Barking and Dagenham, where Labour won every single seat in 2022.
While Keir Starmer has most to lose in the capital on Thursday, the Conservatives are also set for a bruising night.
Kemi Badenoch's party is on course to be reduced to a handful of outer London strongholds, leading in just five boroughs: Bexley, Bromley, Harrow, Hillingdon and Kensington and Chelsea.
The Green Party is set to secure 20% of the vote, just a few points shy of Labour, and come first in up to four boroughs
Meanwhile Nigel Farage has been campaigning heavily in rural suburbs like Bexley and Bromley, stealing votes from the Conservatives
The party's hopes that surprise gains in Westminster and Wandsworth look set to be dashed, as they still trail Labour by 11 points and 7 points respectively.
The Liberal Democrats, despite making almost no headway in the capital since the last set of local elections, are still set to remain dominant in the poshest parts of south west London, including Richmond, Kingston and Sutton.
Luke Tryl, UK Director at More in Common, explained: 'The 2026 elections are set to show that the capital is not immune to the electoral fragmentation that has upended politics across the country.
'Former Labour strongholds look set to see major Green gains with the potential the party controls or emerges as the largest party in a whole swathe of inner London.
'While the Greens advance in Labour's heartlands, Reform looks set to do the same in outer-London boroughs such as Bexley that were previously safe for the Conservatives.
'Add in gains from Independents and it could well be that the electoral map of London we see on May 8th looks totally unrecognisable to what we have become used to.'
A Labour source told the Mail: 'The Greens would result in councils of chaos across the capital. Zack Polanski has the wrong plan for London, and the wrong plan for Britain.
'We'll continue to fight for every vote. The only poll that matters in on Thursday 7 May.'