Conservative Conference: Polls reveal mountain David Cameron has to climb to win 2015 election

The prospect of “more austerity” is the biggest single factor putting off potential Tory voters, the party’s millionaire pollster Lord Ashcroft has admitted, after two new surveys of marginal seats revealed the mountain David Cameron has to climb to win another term in No 10.

A survey by ComRes for ITV News found that Labour has a lead of 11 points in the 40 most marginal Labour-Conservative constituencies – compared with a national lead of around four points. Meanwhile, a poll of Tory-Lib Dem marginals for Lord Ashcroft revealed that the two parties are on a level-pegging, with 32 per cent of the vote each.

Lord Ashcroft said on Sunday that this was a “rather concerning result for the Conservatives”, who need to win a large number of Lib Dem seats to balance those the party expects to lose to Labour. This result represents an overall swing of just 2 per cent to the Tories since the election.

Equally damaging to the Tories were the results from polling in Labour-Lib Dem marginal seats, which found an overall swing of 12 per cent from Lib Dems to Labour. With these findings replicated next year, the Lib Dems would lose most of the seats they are defending against Labour.

At a fringe meeting where he presented the poll results, Lord Ashcroft said: “The prospect of more austerity is the biggest single barrier to voting Conservative next year.”

He added that the party was in the difficult position of trying to present two different messages to voters – that the economic situation is “so bad that the cuts must continue” while “good times are just around the corner”.

“It’s a tough sell,” he said. Lord Ashcroft, who said he would only contribute “bits and pieces” in financial terms to the Tories’ election campaign, added that he didn’t think the Conservatives could win with ad campaigns and political announcements from the centre. “It is a very uphill struggle,” he said. “We cannot win an air war against Ed Miliband. Waffle from [Conservative] central office is not going to work.”

Lord Ashcroft, who until 2010 was one of the party’s biggest donors, told members: “The Conservatives can afford to lose no more than 22 seats to Labour before they cease to be the largest party in the House of Commons.

“Unfortunately, the polling I have already done in individual seats, starting with the most marginal, shows the Tories already behind in 24.”

But in better news for the Conservatives, only just over a third of voters in the seats surveyed by Lord Ashcroft said they would rather see Ed Miliband as prime minister.

And despite Boris Johnson’s popularity, more residents in marginal constituencies think he would make a bad prime minister (43 per cent) than think he would be good (32 per cent).