Full YouGov poll results

Labour has slumped to its lowest poll rating since 1983, when Michael Foot was leader, as voters delivered a withering verdict on last week’s budget.

Gordon Brown’s party slipped to 27% – 16 points behind the Conservatives – amid growing concern about the government’s economic competence, a YouGov survey for The Sunday Times shows today.

If the results of the poll were repeated in a general election, David Cameron would storm into Downing Street with a landslide majority of 120 and a string of high-profile cabinet ministers including Alistair Darling, the chancellor, would lose their Commons seats.

The Conservative lead is the largest of any survey since October 1987, shortly after Margaret Thatcher’s final election victory and on the eve of the Black Monday stock market crash.

Labour’s percentage of the vote is the lowest since June 1983. The YovGov poll, the first since Wednesday’s budget statement, puts the Tories on 43% and Nick Clegg’s Liberal Democrats on 16%.

Brown’s personal approval level has also taken a hit. His minus 26 rating is the lowest since he became prime minister. The poll is equally devastating for Darling. Almost half of voters – 47% – say the chancellor is “not up to the job”. He is backed by barely one in five.

The Tory lead has widened significantly since the last Sunday Times poll a month ago. Then they were ahead of Labour by just nine points.

The main cause of the swing to the Conservatives is the collapse in faith in Brown and Darling’s stewardship of the economy. Just 21% of voters now say they would trust Labour more than the Conservatives to raise their family’s living standards, with the Tories in a decisive lead on this issue.

The overwhelming majority – 83% – believe the economy will either grow more slowly over the next 12 months or slide into recession. Worryingly for Labour, its claims that taxes cannot be cut without harming essential public services are no longer widely accepted.

Six out of 10 back the Tory argument that making the public sector more efficient will create room for lowering the tax burden and almost eight out of 10 – 78% – say the government is not doing enough to cut the amount of taxpayers’ money it wastes.

There was widespread scepticism about Darling’s individual tax rises. Three out of four or 74% agreed that so-called “green” taxation on polluting cars and flights were a “con” and 85% say the higher alcohol duty rates will do nothing to curb binge drinking.

Today’s poll result suggests a possible Labour meltdown in May’s local and London elections. The Tories are ahead of Labour in the capital by 24%, indicating that Ken Livingstone, the Labour mayor, will struggle to hang on to power.

The growing Conservative lead also makes it less likely that Brown will call an election next year.

If the Tory 16-point lead is repeated in the next general election, Jacqui Smith, the home secretary, would be certain to lose her Redditch seat and Ruth Kelly, the transport secretary, would be ousted from Bolton West. Assuming the swing against Labour is the same throughout the country, even Darling’s Edinburgh South West seat would fall to the Tories.

The massive Conservative lead is likely to prompt more insurrection from Labour’s modernisers, impatient with Brown’s failure to reform public services.

Writing in today’s Sunday Times, Alan Milburn, the Blairite former health secretary, warns that Labour is at risk of losing power. “The next election is up for grabs,” he said. “After a string of bad luck and some self-inflected wounds, Gordon Brown is down but not out.”

In his first article on British politics since Brown became prime minister, Milburn accuses Brown of “inconsistency” and urges him to give more power to ordinary citizens. “Whitehall’s grip tightens not loosens through a frenetic outpouring of initiatives ranging from regulating children’s play to banning light-bulbs,” he writes.

Milburn urges Brown to ape Tory plans to allow parents to control school budgets: “Record numbers of parents are seething because they cannot get their child into their preferred school.”

The threat of defeat at the polls could also lead to a revolt from the left, who believe Brown has not done enough for Labour’s “heartland” voters.

If Labour does perform poorly in May, this autumn’s party conference in Manchester threatens to become the scene of internecine plotting. Some MPs are considering challenging Harriet Harman, the Labour deputy leader, a long-standing Brown ally.

Allies of Jon Cruddas, the left-wing backbencher who came third in last year’s contest for deputy, want him to mount another bid for the job.

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