London: Nearly half of voters in UK swing seats may still change their minds about who to vote for in next week's election, an opinion poll published on Thursday showed, suggesting the outcome is still wide open.

The latest Reuters Ipsos MORI poll of "marginal seats" — ones held by ruling Labour that the opposition Conservatives need to win to triumph at national level — suggested no party would win an overall parliamentary majority on May 6.

The survey found that 46 per cent of voters said they had not made a final decision about who would get their vote.

"I could definitely still be swayed," said Peter Marshall, a young voter in Ipswich, a marginal seat in eastern England.

The level of indecision is almost unprecedented at this stage of an election campaign.

Usually, only about a quarter of people are still undecided with a week to go to polling day.

The new poll found that those tending towards a Conservative vote were most certain of their choice.

Of all those expressing a preference for the Conservatives, 65 per cent were sure that they would no longer change their minds.

Only 51 per cent of those tending towards a Labour vote had the same level of certainty, while for the third-biggest party, the Liberal Democrats or Lib Dems, the figure was 42 per cent.

Two in five of the undecided voters polled said they could switch to the Lib Dems, while one in five could still be won over by Labour or the Conservatives, also known as the Tories.

"I'm tempted by the Lib Dems," Marshall said.

"I've got nothing against the Conservatives and (party leader David) Cameron has carried himself well, but I'm thinking about it. It's between the Tories and the Lib Dems."

Short of majority

Voting intentions in the constituencies polled were: Labour 38 per cent, Conservatives 35 per cent and Lib Dems 21 per cent.

That represented a swing of 5.5 per cent to the Conservatives from Labour compared to the last election, in 2005.

The poll indicated the Conservatives would grab 75 seats from Labour to become the largest party in Parliament, but fall short of the 117 seats they needed for an absolute majority.

Some 71 per cent of voters now expect a "hung parliament" without a single party in control. The figure was up from 55 percent in mid-March.

A small majority said this would be a bad thing for the country, which last experienced a hung parliament in 1974.