IMMIGRATION is a more important influence on the voting decisions of Conservatives than of any other group.

The first of the daily Times/ITV News tracker polls confirms the strong Labour position and the significance of immigration for the Tories.

Labour leads on 39 per cent, with the Tories on 33 per cent, the Liberal Democrats on 21 per cent, and other parties on 7 per cent. The poll, based on interviews from April 15-18, differs only slightly from the Populus poll in The Times yesterday which put Labour on 40 per cent and the Tories on 31 per cent. This was conducted from April 14-17.

The main non-internet polls show that Labour is heading for a big Commons majority, with the Lib Dems several points ahead of where they stood at this stage in 2001.

Nearly a fifth of Tory supporters (19 per cent) say party positions on immigration and asylum-seekers are the biggest influence so far in deciding their vote. This compares with 6 per cent of Labour voters and 12 per cent of Lib Dems.

Immigration is much more important for men (15 per cent) than women (9 per cent) and for skilled manual workers (17 per cent) than for professionals and managers (7 per cent).

However, positions on public services such as the NHS are the biggest single influence, on 26 per cent; especially for women (30 per cent) and Labour voters (34 per cent), though least for Tories (20 per cent).

The biggest other influences are opinions of Tony Blair (17 per cent), tax and public spending (15 per cent) and a negative opinion of other parties (9 per cent).

Charles Kennedy has made a more favourable impact than the other leaders so far. Nearly a third say that they like him more than before and a quarter trust him more, compared with a fifth in both cases for Mr Blair and Michael Howard.

Some 44 per cent of voters say that they know more about what Mr Howard stands for than before, slightly more than for the other two leaders. But knowing Mr Howard better has not helped him. Nearly a third think Mr Blair a stronger leader than they did before.

• Populus interviewed a random sample of 1,424 adults aged over 18 by telephone from April 15-18. Interviews were conducted across the country and the results have been weighted to be representative of all adults. Populus is a member of the British Polling Council and abides by its rules. See www.populuslimited.com for more details.

Times Recommends

• Charles blazes trail as sun king
• Thalidomiders win payout 50 years on
• Libel gag on talk of 'medical hurricane'