Gordon Brown will this week go into his toughest parliamentary test since becoming Prime Minister while at his lowest ebb in the polls, according to a survey.
An ICM poll for the Sunday Telegraph newspaper put the Conservatives on 42% and Labour on just 26% - the lowest ever recorded for the party by the company. Nick Clegg's Liberal Democrats are just five points behind Labour on 21%.
But the poll found strong public support for Mr Brown's call for 42-day pre-charge detention for terror suspects, which will be put to a knife-edge vote on Wednesday in what threatens to be his first Commons defeat as PM.
Some 65% of those questioned backed his plan to increase the maximum detention before charge from 28 days to 42, against just 30% who supported Tory leader David Cameron's position of retaining the existing limit.
But Mr Brown's hard-line approach does not seem to have produced dividends with the voting public, with 32% saying that the Tories had tougher policies on terrorism compared to 28% for Labour.
Earlier, the Prime Minister had written to all Labour MPs in the hope of heading off a rebellion in the Wednesday vote.
Restating safeguards drawn up by Home Secretary Jacqui Smith to ensure that the new power is not used in an arbitrary fashion, Mr Brown assured MPs that ministers had done "everything in our power" to balance civil liberties with the need to tackle terrorism.
"The challenge has been to make sure that, through proper judicial and parliamentary oversight, we both keep the public free from the threat to our security, and secure the fundamental liberties of the citizen," he wrote.
Former Prime Minister Sir John Major said the 42-day issue now appeared to be more about proving Mr Brown's "virility" than about the merits of the policy.
Renewing his assault on the 42-day detention plans, Sir John said that Ms Smith's amendments had left the proposals "messy" and possibly unworkable.
