The poll - carried out on Thursday - shows Mr Heseltine for the first time moving ahead of the Prime Minister as the public's favoured Conservative leader. The other main challenger - the Chancellor, Kenneth Clarke - has been left well behind.
NOP puts Labour voting support at 50 per cent for the first time since 1990. The Tories are at 26 per cent and the Liberal Democrats on 20 per cent.
The poll - taken after last week's call from the backbench Tory MP Tony Marlow for the Prime Minister's departure - will increase pressure on Mr Major, who yesterday insisted he would stay in Downing Street. He told reporters in his Huntingdon constituency that politicians had to be prepared to take rough knocks and added: 'I have got a programme. I believe in that programme. I am not going to be knocked off it.'
Asked if he would stand aside if senior party figures told him Mr Heseltine would make a better leader, the Prime Minister replied: 'They haven't'
However, a survey of 100 Conservative MPs in today's Sunday Times shows that 41 believe Mr Major will not lead them into the next election; 40 think he will and 19 don't know.
A quarter say they want Mr Major to stand down. Of those MPs prepared to name an alternative leader, 26 backed Mr Heseltine, 10 supported Michael Portillo, Chief Secretary to the Treasury, six Mr Clarke, and three John Redwood, Secretary of State for Wales. The results suggest that the poll may have included a disproportionate number of right-wing MPs.
If NOP's figures are reflected in May's local council elections, June's European elections and the Eastleigh by- election, they could provoke panic in Conservative ranks.
NOP shows that, with Mr Heseltine as leader, 30 per cent of those polled would back the Conservatives. Mr Clarke and the Foreign Secretary, Douglas Hurd, encouraged support from 24 per cent of voters, fewer than the Tories have now. Only Baroness Thatcher, who is unlikely to make a political comeback, fared better, increasing Conservative support to 31 per cent.
In February an ICM poll for the Guardian showed that fewer people would vote Tory if Mr Major was replaced by Mr Heseltine or any of his colleagues. The change since then indicates that the President of the Board of Trade may have begun a surge of popularity timed perfectly for a November leadership crisis.
Forty-nine per cent of those surveyed believe Mr Major should stand down. This includes 40 per cent of those who voted Tory in 1992 and 30 per cent of those who would still vote Tory now.
A Gallup poll in today's Sunday Telegraph says that 65 per cent think Mr Major should stand down - but the sample of 655 people compares with NOP's 1,135.
The NOP poll suggests that Mr Heseltine would bring the Tories only a modest number of extra votes. But some MPs, particularly in south-west England, will note that he performs particularly well among people who say they voted Tory in 1992 but would vote Liberal Democrat now. NOP suggests that he would bring more than one in three of those people back to the Tory fold.
Yesterday a third Conservative backbencher hinted that he may soon call for Mr Major's resignation, following the calls made last week by John Carlisle, MP for Luton North, as well as by Mr Marlow, MP for Northampton North. Sir Richard Body, MP for Holland with Boston, said: 'It is not healthy for the Government to have the leadership constantly at issue. I am going to have a meeting with the officers of my local association. If we are all agreed about what should be done, then we shall do it.'
Speculation continued last night that the former Chancellor, Norman Lamont, or the former Home Secretary, Kenneth Baker, might stand against Mr Major in the autumn, but the Prime Minister will not give up without a fight. Downing Street, conscious that people remain gloomy about their own and the country's economic prospects over the next 12 months, has held several internal meetings about how to re-create a 'feel good' factor without fuelling inflation.
Sir Norman Fowler, the party chairman, told journalists last week that the Conservatives planned to appoint between 40 and 50 full-time agents in marginal seats. Sir Norman added that it was inconceivable that the party would want a leadership contest this year.Reuse content