Tories target 'extraordinary' win

David Davis was interviewed by Andrew Marr

The Conservatives are "pulling out all the stops" to win Thursday's Crewe and Nantwich by-election, shadow home secretary David Davis has told the BBC.

Polls suggest a first by-election gain since 1982 is possible - Mr Davis said a win would be "quite extraordinary".

Labour's Harriet Harman said there was no point in "second guessing" the result but admitted their class-based campaign was not the "most positive".

She said it was designed to boost their candidate, not demonise the Tory one.

Her comments on the BBC's Politics Show came after fellow Labour minister, Ed Miliband, defended the class-based attacks as "typical" of the stunts and "adventurous ways of campaigning" seen in by-elections.

Meanwhile, with the by-election campaign nearing its end, Lib Dem leader Nick Clegg told BBC Radio 4 he thought his party could win it.

He said the Labour vote was collapsing and that people were not turning to the Conservatives after asking questions about the "substance" behind their "rhetoric".

Harriet Harman on Labour's by-election campaign

Mr Davis told BBC One's Andrew Marr Show: "We have got a 7,000 majority to overturn.

"We haven't won a by-election from Labour in 30 years. But we are pulling out all the stops."

Asked about the broader political picture, and Mr Brown's difficulties, Mr Davis said he had been surprised.

"I was the Jeremiah in the Tory party. I said, 'watch this man, be careful, he's dangerous'. And for the first three months it looked like I was right.

"But actually the number of unforced errors he has made has been quite extraordinary in truth - quite extraordinary."

We have got to get Britain through the economic difficulties it faces and we have got to go out and fight for what we believe in Ed Miliband Cabinet office minister In full: By-election candidates

Mr Davis was speaking after an ICM poll for the News of the World suggested that 45% of people in Crewe and Nantwich were planning to vote Conservative, with 37% for Labour.

Meanwhile a national YouGov poll for the Sunday Times put the Conservatives on 45%, with Labour on 25% and the Liberal Democrats on 18%.

Cabinet Office minister Ed Miliband said that the polls were bad, but insisted that Labour could turn them round.

Unique MP

He told Sky's Adam Boulton: "We have got to get Britain through the economic difficulties it faces and we have got to go out and fight for what we believe in.

"I am confident that if we do that, we can turn round the opinion polls."

Ministers and shadow ministers are expected to keep up their visits to the constituency this week ahead of voting.

Mr Miliband insisted Labour had fought a good campaign, saying: "Our central campaign in Crewe and Nantwich is about Gwyneth Dunwoody being a unique MP and Tamsin Dunwoody (her daughter) being the best person to take forward Gwyneth's legacy."

Edward Timpson will fight the seat for the Conservatives, while Elizabeth Shenton will stand for the Liberal Democrats. In all there are ten candidates.

At the 2005 General Election Gwyneth Dunwoody was elected with 48.8% of the vote. The Conservatives came second with 32.6% of votes. The Lib Dems came third with 18.6% of votes.