A Populus poll for the Times suggests that the two main parties may win no more than half the total votes cast in Thursday's local and European elections.

Turnout may be about a third of the eligible electorate, with Labour and the Conservatives together winning the backing of about one in six adults.

The Liberal Democrats, in third place, and the UK Independence Party could gain more members of the European parliament.

According to the survey, Tory support in the European elections could fall from 36 per cent in 1999 to around 24 per cent.

Labour could slip from 28 to between 25 and 26 per cent, while the Lib Dems are on course to achieve between 16 and 18 points.

The UKIP could see its support rise from seven to around 13 per cent, implying an increase on its present total of three MEPs.

The figures come as problems with the government's postal voting pilots continue to emerge.

Thousands of electors have had their votes sent back after returning officers found the forms had not been properly completed.

It also emerged that one council involved in an all-postal ballot has had to set up emergency polling stations because up to 5,000 voters had not received their forms.