THE fear factor about a minority Labour government being propped up by the SNP, which has been promoted heavily by David Cameron and his Conservative colleagues, is beginning to cut through south of the border, according to a Comres poll.

The snapshot showed that in the 50 most marginal Tory-held seats, 58 per cent of people were worried about the influence Nicola Sturgeon and her colleagues could have on an Ed Miliband government.

Indeed, 47 per cent made clear the Nationalists should be "kept out" of a UK Government while 62 per cent felt a Lab-SNP alliance would not be good for Britain.

The pollster said: "This narrative provides a source of hope for the Conservatives in the final few days of the campaign with three in 10 of those currently intending to vote Labour - 28 per cent -saying that it is important to keep the SNP out of the UK-wide government; seven in 10 of those currently intending to vote Conservative - 71% - say the same."

Voters in these 50 Conservative-held marginals were more likely to think another Tory-Lib Dem coalition would be good for Britain - 34 per cent - compared to a Labour government supported by the SNP - 23 per cent.

Generally in the 50 marginals, Labour was three points ahead of the Conservatives on 40 points. However, 27 per cent of people polled said they had still to make up their minds who to vote for.

In another survey, conducted on behalf of Lord Ashcroft, the Tories were two points ahead - 34 to 32 - in Thanet South, the Kent seat being targeted by Ukip leader Nigel Farage. The polling suggested Labour voters were prepared to lend their votes to the Tories to keep him out. But the margin means it remains too close to call.

In Sheffield Hallam, which Nick Clegg represented in the last parliament, Labour's lead was down to one point, compared to three in November. While 30 per cent of 2010 Lib Dems said they were planning to vote Labour next week, a similar proportion of Tory voters said they would vote Lib Dem.

It has been suggested Tory HQ is doing very little in the constituency to help Mr Clegg survive should Mr Cameron need to call on the Lib Dem leader to form another Lib-Con partnership.