Voters turned their back on Labour in droves as Conservative candidate Edward Timpson turned a deficit of 7,000 votes into a Tory majority of 7,860.

With the Government reeling from the 10p tax row and anger over soaring food, fuel and energy prices, the Tories gained their first seat at a by-election since 1982. The swing of 17.6 per cent would be enough to give them a Commons majority of more than 300 if repeated at a General Election.

As pressure mounted on Prime Minister Gordon Brown Mr Cameron travelled to Crewe to congratulate his new MP before addressing the party's Scottish conference in Ayr, pledging to use the triumph as the platform for building a "coalition for change" to sweep Labour out of power.

He said thousands of people who had never voted Tory before did so in Crewe and Nantwich, where the Liberal Democrats made little ground as they were squeezed by the two main parties.

"I want to say to those people we will do everything over the coming months and years to earn their trust and hold their trust, to go on reaching out to more people who never voted for our party in the past," he said.

Mr Cameron attacked Labour's negative campaign in Crewe and Nantwich – where they portrayed Mr Timpson as a "toff" – saying it marked "the end of New Labour".

While the Tories celebrated winning the by-election – prompted by the death of Labour MP Gwyneth Dunwoody – Mr Brown faced fresh scrutiny of his leadership after a month which saw a mauling in the local and London mayoral elections and his Chancellor, Alistair Darling, was forced to borrow £2.7bn to end the 10p tax row.

Backbencher Graham Stringer, a former Government Whip, said there was now a "real debate" within the party as to whether it was better to get rid of Mr Brown or to hope Labour's fortunes would pick up, urging Cabinet Ministers to challenge him.

Selby MP John Grogan said the Government was in "a fight for our political lives" and urged Mr Brown to bring Blairite heavyweights such as Charles Clarke back into the Cabinet along with Left-wingers such as failed deputy leadership candidate Jon Cruddas.

But Rotherham MP and former Europe Minister Denis MacShane said the defeat was merely the restoration of "the laws of by-election political gravity" and urged colleagues to keep quiet.

"The more they blabber, the worse Labour looks to the voters," he said. "Those calling for leadership elections are playing into Tory hands."

Mr Brown, who made a show of carrying on with business as usual with a visit to meet staff at a London hospital, brushed aside questions about his leadership.

But loyal Ministers rallied round the Prime Minister, with Cabinet Office Minister Ed Miliband insisting he was the "right leader".

The MP for Doncaster North said he was "absolutely confident" the Government could recover from the current economic turmoil. "We have got the right leader, we elected the right leader unopposed last year and we have got the right leader to take us into the General Election," he said.