Chris Davies, the new MP for the constituency, said "Blairism has failed its first test", while Labour claimed its close second place meant it could not be counted out of contests anywhere in the country.
Paddy Ashdown, the Liberal Democrat leader, said Labour's campaign tactics belied the "new politics" of mutual respect that he thought Tony Blair believed in: "I know that a number of Labour members are thoroughly ashamed by the Labour Party's campaign. I think Labour should let the dust settle a little and then reflect on whether they want this style of politics in Britain."
Mr Ashdown's comments suggest that, after a recent warming in relations between the opposition parties, lasting damage has been done.
Peter Mandelson, the Labour campaign manager, said Labour is still open to "dialogue" but that this does not preclude fierce electoral competition.
Mr Davies, elected on Thursday with a 1,993 majority over Labour, said his opponents had "brought over the very worst elements of American political tactics". He said Labour was "drifting so far to the right it's an astonishing transformation".
Phil Woolas, the Labour candidate, and Mr Mandelson, the MP for Hartlepool, were unapologetic at their rival morning-after news conference yesterday. "The result is a huge vindication of our campaign," said Mr Woolas. Labour's hard tactics had exposed Liberal Democrat weakness, he added: "When their policies are put under the spotlight they crumble."
Mr Davies conceded that Labour's tactics, accusing him of being "high on tax and soft on drugs", had been effective. "The thing about American- style negative campaigning is that it works," he said.
He also appeared to concede Labour had been justified in raising the drugs issue by claiming in his speech after the result that the people of Littleborough and Saddleworth had voted for a Royal Commission to review the law on drugs. Asked again whether he supported the decriminalisation of cannabis, he said: "I don't know. I don't pretend to have the answers. That's why I want a Royal Commission to look at it, to take it out of politics."
Mr Mandelson claimed that the by-election marked a breakthrough for Labour. He said Labour would have won if the campaign had lasted a week longer. "The Liberal Democrats have been fighting here for 10 years and nearly lost. We've been fighting for a little over three weeks and nearly won," he said.
It is true that Labour has advanced significantly since Eastleigh, a by-election in June last year where the party started in a similar third place. There, Labour came second and narrowly avoided coming third. On Thursday it nearly won.
The psychology of future by-elections, and of the general election, has been transformed, increasing the number of seats which Labour can realistically hope to win from third place.
Conservative Party chairman, Brian Mawhinney, claimed the result reflected "the first stirrings" of a swing back to the Tories by the voters following John Major's leadership victory. The Tory share of the vote, 24 per cent, was just below that at Eastleigh. But the fall in the Tory share was smaller.
John Hudson, the Tory candidate, said the swing against him was the smallest since the Kincardine and Deesside by-election in November 1991.Reuse content