GORDON BROWN is facing a cabinet revolt over controversial new terror laws amid concern in the government about an unprecedented collapse in his authority.

Brown’s personal rating has plunged further and faster than any other British leader since political polling began in the 1930s, a new poll for The Sunday Times reveals.

The double blow came as the prime minister’s allies moved to quash speculation that his plummeting popularity could prompt a plot to remove him from office.

The cabinet dispute centres on Brown’s determination to push through legislation extending the maximum period terrorism suspects can be detained without charge to 42 days. Jack Straw, the justice secretary, has told Commons allies that he has reservations about the policy, which critics say will inflame tension among Muslims and lead to miscarriages of justice.

“Jack understands that the bill as it stands is seriously flawed,” said a Labour colleague. “It is no accident that in public he has so far been silent on the issue.”

In another blow, Geoff Hoon, the chief whip, has told Brown that he will lose next month’s Commons vote unless concessions are made. “As it stands, Gordon will go down by 30 votes,” said a minister. “In the current climate, his leadership might not survive that blow.” Downing Street sources insisted last night that no further concessions were planned.

Today’s YouGov poll for The Sunday Times puts David Cameron’s Tories on 44% - the party’s highest level of support since 1992. They lead by 16 points over Labour on 28%, while the Liberal Democrats are on 17%. Only 11% now believe that Labour will win a clear victory in the next general election.

Brown’s poll rating has fallen to minus 37, down from plus 48 last August. The collapse is the most dramatic of any modern-day prime minister, worse even than Neville Chamberlain who in 1940 dropped from plus 21 to minus 27 after Hitler’s invasion of Norway.

Brown appeared to be losing the support of some of his oldest political allies. Geoffrey Robinson, the former Treasury minister, joined the revolt over the scrapping of the 10p starting rate of income tax, which critics say has unfairly hit low-paid workers. “It is hurting many people whom the government never set out in any of their policies to hurt,” he said. Tessa Jowell, the Olympics minister, acknowledged that the rebels were providing a “reality check”.

Blairite former ministers are expected to speak against Brown’s “dithering” leadership style after the May 1 local council elections. “We are totally inept,” one minister said.

Allies of Ed Balls, the schools secretary, were forced to issue a statement denying he was running a secret leadership campaign. There have been claims that Balls has been positioning himself to succeed Brown if he is forced out before the next election.

In the statement, Lord Adonis, Balls’s junior minister, said: “Over the past nine months we have been driving forward Labour’s education reforms under Ed’s leadership. The idea that these important reforms can be dismissed as political games or positioning is just ridiculous.”

Allies of Brown are urging him to hold a snap cabinet reshuffle if Labour does badly in the local elections. “The only thing that will persuade voters he is serious is blood on the No 10 carpet,” said a minister.

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