The yawning gap between Labour and the Conservatives is the biggest in a YouGov survey of the capital for at least 12 years.
If maintained at a General Election, it could see the Tories haemorrhage eight seats in the city, leaving them with just 13 London MPs.
In a series of other damning findings, it also showed that two thirds of Londoners believe the Prime Minister should resign.
Four out of five think Mr Johnson has not been honest in responding to the allegations of Downing Street parties during lockdown, including 69 per cent of 2019 Conservative voters.
As he fought for his political life, the PM told MPs last week that he believed a “bring-your-own-booze” party on May 20, 2020, in the garden of No10 when Britain was in lockdown was a “work event”.
He said he went into the garden to thank staff before going back into his office 25 minutes later.
However, nearly three quarters of Londoners believe his assertion that he thought it was a work event is “not an honest account”.
Around the same proportion of Londoners say the Metropolitan Police should investigate the string of parties in No10 when the nation was under Covid restrictions.
The poll put Labour on 55 per cent in the capital, with the Tories on 23 per cent, the Liberal Democrats nine per cent, Greens seven per cent and Reform UK three per cent.
YouGov polls going back to early 2010 showed it was the biggest gap since then and it compares to a Labour lead of 18 to 19 points last spring.
In Inner London, Labour now has a 43-point lead (61 per cent compared to 18 per cent) and in Outer London it is 26 points ahead (51 per cent v 25 per cent).
Patrick English, Political Research Manager at YouGov, said: “Clearly, this poll is not good news for the Prime Minister and the Conservatives in London.
“It is the largest Labour lead we have seen in the capital since at least 2010, and if it were replicated at a General Election the Conservatives could lose as many as eight constituencies, leaving them with just 13 London MPs.
“Labour might gain up to six seats, increasing their London total to 55, while the Lib Dems would move up to five.”
The findings will also alarm Conservative councillors across London staring at potentially disastrous local elections in May if their party fails to recover in the polls.
The survey came amid speculation at Westminster that 54 Tory MPs were Wednesday morning on the brink of handing in letters, of no confidence in the PM, to Sir Graham Brady, chairman of the 1922 Committee of backbench Tory MPs, which would trigger a vote in Mr Johnson’s future.
Key findings in the poll include:
- Sixty-seven per cent of Londoners believe Mr Johnson, a former Mayor of London, should quit as PM, including 42 per cent who backed the party at the 2019 General Election.
- Eighty per cent believe the Prime Minister has not been honest in responding to questions about allegations of parties in Downing Street during the lockdown period, including 58 per cent of current Tory supporters.
- On Mr Johnson’s statement that he believed the gathering on May 20 was a working event, 72 per cent think this was not an honest account, including 56 per cent of Tory voters in 2019.
- Seventy-four per cent believe Scotland Yard should probe potential breaches of Covid rules in Downing Street, including 57 per cent of Conservative backers in the 2019 General Election
- Eighty-three per cent believe the May 20 party, as described by the Prime Minister, was not acceptable under the then lockdown rules, including 74 per cent of Tory 2019 voters.
- YouGov interviewed 1,166 adults in London between January 13 and 17. Data are weighted.
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