The poll -- done by YouGov for the Times of London -- comes just ahead of a crucial by-election in Crewe & Nantwich, which has been represented for 34 years by Labor stalwart Gwyneth Dunwoody. Losing it would be embarrassing to the party, political analysts say.

The YouGov poll found that 45 percent of the national electorate favors the Conservative Party, giving it a 20-point lead over Labor. Labor's share has dropped 4 points in a months, while the Conservatives and the Liberal Democrats are both up 2.

Only 17 percent of those surveyed said Brown is doing a good job, while 78 percent said he is not. Almost six out of 10, 59 percent, said Brown should resign before the next general election.

Only 21 percent said Brown is capable of doing the job of prime minister, while 69 percent said he is not up to the job.

Eight percent said Brown might be able to lead Labor to another electoral victory. Only 14 percent think Labor could win with another leader.