Despite doubts about the honesty and trustworthiness of Tony Blair, the public still prefers him to Michael Howard as a prime minister, according to a new poll.

Some 44 per cent of those quizzed believe Blair is "slippery" and "a liar", the ICM survey in the Guardian on Thursday found.

Yet the same number feel he would make the best man in Downing Street, while 55 per cent see him as charismatic.

Just 22 per cent rate the Conservative leader as the best prime minister, even though he is seen as more trustworthy.

Only 24 per cent believe Howard is charismatic. But fewer people, 29 per cent, believe he is "a liar" than have the same opinion of Blair.

However, 42 per cent also see the Tory chief as "slippery".

With the Conservative election campaign concentrating heavily on Blair, accusing him of having misled parliament and the public over Iraq and tax, the findings suggest the strategy may be backfiring.

As Howard is equally unpopular on many counts, the Tories may be wasting their money and efforts on personal attacks.

Blair's rating as the best prime minister has gone up six points in the past week, during which Howard has stepped up his criticism and become more prominent himself.

Overall, the poll puts Labour on 40 per cent, up one on last week, the Conservatives unchanged on 33 per cent and the Liberal Democrats down two on 20 per cent.

With one week to go until polling day, a similar result would give Labour a majority of at least 120 seats.