The adjusted figures in our poll put Labour on 53 per cent, the Tories on 32 per cent and the Liberal Democrats on 10 per cent.
Our findings come on the same day as a Gallup poll for today's Daily Telegraph showing a dramatic widening in Labour's lead from 15 to 26 points, which is unlikely to reflect a real movement of opinion.
However, there is certainly no sign of Labour's lead weakening in the wake of last week's victory in the Wirral South by-election.
In our survey, 62 per cent of Labour voters say they will "certainly" vote Labour, while only 50 per cent of those who intend to vote Tory say they will certainly do so.
Conversely, 17 per cent of Tory voters admit that they might change their mind about how to vote, against only 12 per cent of Labour voters. The findings scotch the theory that the Labour vote is soft.
Of those currently intending to vote Labour, 12 per cent say they voted Tory in 1992 and 6 per cent say they have switched from the Liberal Democrats.
On the other hand, the finding may reflect the well-established reluctance of Tory supporters to identify themselves - a bias which contributed to the failure of opinion polls at the last election.
Like the other polling companies, Harris has adjusted its "raw" figures by reallocating don't-knows and people who refuse to say how they intend to vote, to the party they say they voted for in 1992. This has the effect of cutting Labour's share of the vote by two points and adding two points to the Tory vote.
Our poll's findings are in the same range as those of the other main polling companies - the average Labour lead is currently 18 points. One of the main differences is that it gives the lowest figure for Paddy Ashdown's Liberal Democrats - who according to ICM are running at 16 per cent, not much lower than their 18 per cent share of the vote in the 1992 election.
The figures for how people say they voted in 1992 are also a useful cross- check on the broad reliability of the poll, and they show a Tory lead of one point, as against the actual 7.5-point margin of John Major's victory. This is about what would be expected, given that people tend to "mis-remember" voting for the party they support now.
Our poll also asked a series of questions about people's attitudes to the possibility of cloning human beings. Detailed analysis of the figures reveals that older people and women are markedly more hostile to the idea. Of women, 78 per cent thought human cloning should never be allowed and all research into it stopped, against 66 per cent of men; and 80 per cent of over-55s were totally opposed, against 66 per cent of under-35s.
Con 32% Lib Dem 10%
Sample: 1,009 Fieldwork: 28 February - 3 March
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