The Birmingham MP responsible for branding a Conservative candidate a "toff" in Labour's controversial by-election campaign has insisted he has the backing of the Prime Minister .

Steve McCabe (Lab Hall Green) defended himself following reports that senior Labour figures were angry about the direction of the party's campaign in the Crewe and Nantwich by-election.

He was appointed by Gordon Brown to oversee Labour's efforts to hang on to the seat, following the death of long-serving MP Gwyneth Dunwoody.

But colleagues are reportedly concerned about the tactics being used, as the party struggles to hold on to a majority of 7,078. Victory for David Cameron's Conservatives would be another blow for Mr Brown following a series of dramatic Tory gains in local elections earlier this month.

Labour has focused on the background of Conservative candidate Edward Timpson, son of the founder of the shoe chain, mocking him as a "Tarporley toff" - a reference to the leafy village of Tarporley where he lives.

One Labour leaflet, focusing on youth crime and regeneration, asked voters: "Do you really think a Tory toff from Tarporley cares?" Labour activists dressed in top hat and tails have also shadowed Mr Timpson as he campaigned in the constituency.

But there has been increasing concern among Labour figures at Westminster that the tactics could backfire, according to reports.

Asked over the weekend if Labour was running a positive campaign, Harriet Harman, the deputy leader, admitted: "It's not the most positive campaigning, no."

David Hill, who was Downing Street communications chief under Tony Blair, said: "What has happened in the campaign is that something supposed to be relatively lighthearted to kick off the campaign has taken off and campaigners have not been able to rein it back in as they should have."

In private, some Labour figures are more outspoken, according to reports. Stephen Carter, the new strategy chief at No 10 is reported to be among those who urged Labour not to attack the Tories on class grounds.

But Mr McCabe insisted the campaign had been misrepresented.

He said: "I do know that the campaign has been characterised by quite a lot of misinformation, largely by our opponents. I think there may be one or two gullible souls who have chosen to believe the Tory propaganda.

"All I can tell you is that people I have spoken to have no problems with what we are doing, none whatsoever."

He added: "The campaign in Crewe has been the campaign in Crewe. It is a by-election campaign, and how the national media chooses to report the opposition's propaganda is up to them. The people I have spoken to, including the Prime Minister, have thanked us for our work and asked us to carry on."

He admitted Labour faced a struggle to hold the seat, saying he expected a close result.

But he said he did not believe the Conservatives would achieve the kind of swing which Labour achieved in the 1990s, before it won a General Election.

"From day one, it has been extremely difficult. We are fighting in a national climate where the Tories are ahead in the polls, and personally I believe the result will be close."

A poll published on Sunday suggested the Conservatives were on course to win the seat, with 45 per cent of constituents planning to back the Tories, compared to 37 per cent for Labour.

This would give the Conservatives a majority of 1,000 over the Labour candidate, who is Mrs Dunwoody's 49 year-old daughter, Tamsin Dunwoody, a former Welsh Assembly Minister.

A separate poll put the Conservatives on 45 per cent of the national vote to Labour's 25 per cent.

Mr Brown has ordered his ministers to descend on Crewe and Nantwich in force this week, in a last-ditch bid to rescue the seat.