LONDON (Reuters) - The Conservatives still lag Labour in crucial marginal constituencies they must win to secure a clearcut election victory, according to a poll commissioned by Reuters.

Conservative party leader David Cameron speaks during his monthly new conference in central London March 23, 2010. REUTERS/Toby Melville

The Ipsos MORI poll shows the Conservatives have cut Labour’s lead in these constituencies, but the swing is not sufficient to guarantee them government after an election expected on May 6. It reinforces the prospect raised in most recent surveys of an inconclusive outcome.

“This is very much hung parliament territory,” said Helen Coombs, Ipsos MORI’s Deputy Head of Political Research.

“Nevertheless, everything is still to play for, since almost half the public, and a third of those who are certain they will vote, say they may still change their mind.”

Because of the way Britain’s electoral system works, winning constituencies or seats is more important than the overall national share of the vote and the Conservatives have poured money into marginals to help ensure victory.

KEY SEATS

The Ipsos MORI poll, based on responses from 1,007 prospective voters in key marginals, shows 41 percent of those who say they are certain to vote in the next election would vote Labour compared to 37 percent who would vote Conservative.

That is a five percent swing to the Conservatives from Labour compared to the last general election in 2005 -- and a better showing for them than nationally. The Ipsos MORI national poll, published on Wednesday, shows a four percent swing.

The Conservatives need a swing of between five and nine percent to secure the marginals.

Ipsos MORI conducted the poll before Labour Chancellor Alistair Darling set out his 2010 budget on Wednesday although initial voter reaction suggested the budget, which was short on detail and long on politics, was likely to have limited impact.

“I’ve got no faith in Labour or the Conservatives,” Ron Wilcox, a 73-year-old pensioner, told Reuters on Thursday.

“They all talk but there’s nothing to back it up.”

Asked what he thought of the budget, Wilcox said: “Not a lot.”

The Conservatives will be hoping to attract more supporters like 46-year-old Nasir Gabrial, a taxi driver in Brighton, an area that has two marginal constituencies, one of which requires a swing of just over seven percent for the Conservatives.

“I voted before for Labour but I will vote Conservative this time,” Gabrial told Reuters. He said the economy was the electoral main issue for him.

“Labour has messed up this country,” he said. “Now there’s no money.”

Despite the preference for Labour shown by voters in marginals, voters in these areas largely believed the Conservatives would end up being the largest party in parliament -- suggesting they are unaware of their power to shape the vote.

This is reinforced by figures showing 75 percent of respondents either believed they did not live in a marginal constituency or did not know whether they lived in one.

“This is true, and highlights the scale of the task that the Conservatives face: to gain a majority they must be able to win in these key seats where Labour won comfortably last time and which would not conventionally be defined as marginal,” Ipsos MORI’s Coombs said.

Labour and Conservative voters are more likely to say they have definitely decided who to vote for than supporters of the Liberal Democrats, meaning there is huge scope for tactical voting by Liberal Democrats in these constituencies.

* Technical Details

- Ipsos MORI interviewed a representative sample of 1,007 adults aged 18+ across 56 marginal constituencies in Great Britain.

- These are Labour-held constituencies which the Conservatives need a swing of between 5 percent and 9 percent to win.

- Interviews were conducted by telephone 19-22 March 2010, before Wednesday’s budget.

- Data are weighted to match the profile of the population.