The new constituency-by-constituency modelling by the pollster YouGov - commisioned by The Times newspaper - showed on Tuesday that the Conservative party could lose 20 of the 330 seats it currently holds and the opposition Labour Party could gain nearly 30 seats.

That would leave the Conservatives 16 seats short of the overall majority of 326 needed to govern without the support of other parties.

It also makes the prospect of a coalition between Labour, the Scottish Nationalist Party (SNP) and Liberal Democrats a realistic possibility, for the first time in this election campaign.

The central projection of the model, which allows for a wide margin of error, would be a catastrophic outcome for Prime Minister May. She called the snap election in a bid to strengthen her hand in negotiations on Britain's exit from the EU.

Not so strong and stable

Seven polls carried out since the May 22 Manchester attack have shown May's lead over the Labour Party narrowing.

A poll conducted by Survation for ITV's Good Morning Britain program showed May's lead had dropped to 6 percentage points from 9 points a week ago and 18 points two weeks ago.

An ICM poll for the Guardian showed May with a 12-point lead, which would be enough for a majority of around 100 but down two points from last week and far from the record 22-point lead earlier in May.

The Survation poll found just over half of the 1,009 respondents thought May would make the best prime minister, while support for Labour's Jeremy Corbyn stood at just 30 percent, albeit higher than in previous surveys.

Jeremy Corbyn attracts supportive, mixed crowds on the campaign trail

Old and young alike

May's decision to set out plans on May 18 to make some elderly people pay a greater share of their care costs - dubbed the "dementia tax" by opponents - is being seen as one reason behind the fall off in support.

May has backtracked on the policy recently and has also appeared irritated when taking questions from reporters.

Labour leader Jeremy Corbyn faces the challenge of a largely negative media , but performed well in Monday's television debate. However, during a radio interview on Tuesday, Corbyn was unable to provide the correct figure for the cost of his party's plan for child care. The incident was shown widely, and comparisons made to previous, similar failures from other party spokespeople which had undermined their credibility.

Labour commands a lead among young Britons, but recent votes show they are the least likely to go to the polling stations.

jbh/jm (Reuters)