Gordon Brown today faces a make or break challenge to his leadership after Labour looked set to slump to just 16% of the national vote in the European elections.
The far-right British National party won its first ever seat in Europe, and the Conservatives topped the polls in Wales.
Another dismal night for Labour saw it pushed into fourth and sometimes fifth place across large swaths of the country.
Early projections suggested the Conservatives would come first, with just under 30% of the vote, the United Kingdom Independence party second, with around 20%, and Labour and the Liberal Democrats would battle it out for third and fourth place.
The BNP won 10% of the vote – more than 120,000 votes – in Yorkshire and the Humber, giving it its first ever foothold in the European parliament. In Wales, Labour lost 12% of the vote, allowing the Conservatives to emerge as the overall winners for the first time since 1918.
In the North East, the first UK region to declare, the state of the parties remained the same, with one seat going to Labour, one to the Conservatives and one to the Liberal Democrats.
Labour's share of the vote was down 9%, the Tories were up 1% and the Lib Dems saw no change.
The state of the parties also remained static in the East of England, with the Conservatives returning three MEPs, Ukip two and Labour and the Lib Dems one each.
However, Labour's share of the vote was down 6%.
Harriet Harman, the Labour deputy leader, described tonight's results as "dismal" for the party, which was pushed into fifth place in the South East with half the votes counted.
Official EU projections indicated that the centre-right parties would emerge as the largest grouping in the European parliament.
Hours before the crucial Euro results were due to be announced, Brown's hopes of survival suffered a further setback when the former lord chancellor, Lord Falconer, became the most senior figure yet to call for a leadership contest.
The peer – once Tony Blair's flatmate – warned that potential candidates were waiting in the wings, ready to mount a challenge, if Brown was not prepared to stand down as prime minister.
Meanwhile, Tessa Jowell became the first member of the cabinet to speculate openly that Brown could be prepared to step aside if he believed he had become an "obstacle" to Labour winning the next general election.
If Labour were to end up coming fourth behind the Liberal Democrats, it could be the catalyst for plotters behind the so-called "peasants' revolt" to show their hand when MPs return to Westminster tomorrow.
Brown sought to rally support with a televised address to a hastily arranged gathering of sympathetic Labour party activists in east London earlier today.
He said the public would not understand if the government gave up at a time when it was faced with tackling the recession and cleaning up parliament.
"What would they think of us if ever we walked away from them at a time of need? We are sticking with them," he said.
"We have a purpose, we have a mission, we have a task ahead. We are going to get on with that task of building a better Britain."
Falconer's call for a leadership contest was swiftly rejected by the newly promoted home secretary, Alan Johnson, who is widely regarded as the most likely successor to Brown if the prime minister is ousted.
"I don't agree that regicide gives you a unified party," he told the Politics Show. "I think that Gordon Brown is the best man for the job."
Earlier, the business secretary, Lord Mandelson, cast doubt on the ability of the plotters to put up a credible candidate against Brown.
"It would require somebody to stand against him, somebody who is raising their standard and saying that they could do a better job ... we don't have that person," he said.
He told rebels to "stop taking shots" at the prime minister and warned that they faced the prospect of having to fight an immediate general election if Brown went.
However, Nick Raynsford, another former minister who has been calling on Brown to stand down, said the party could not carry on as it was.
The flashpoint could come as soon as tomorrow's weekly meeting of the parliamentary Labour party at Westminster, when Brown is expected to address his backbench MPs.
It will be followed almost immediately afterwards by a debate on Labour's future, addressed by the former Europe minister Caroline Flint – who resigned from the government on Friday – and the arch-Blairite Stephen Byers.
The far-right British National party won its first ever seat in Europe, and the Conservatives topped the polls in Wales.
Another dismal night for Labour saw it pushed into fourth and sometimes fifth place across large swaths of the country.
Early projections suggested the Conservatives would come first, with just under 30% of the vote, the United Kingdom Independence party second, with around 20%, and Labour and the Liberal Democrats would battle it out for third and fourth place.
The BNP won 10% of the vote – more than 120,000 votes – in Yorkshire and the Humber, giving it its first ever foothold in the European parliament. In Wales, Labour lost 12% of the vote, allowing the Conservatives to emerge as the overall winners for the first time since 1918.
In the North East, the first UK region to declare, the state of the parties remained the same, with one seat going to Labour, one to the Conservatives and one to the Liberal Democrats.
Labour's share of the vote was down 9%, the Tories were up 1% and the Lib Dems saw no change.
The state of the parties also remained static in the East of England, with the Conservatives returning three MEPs, Ukip two and Labour and the Lib Dems one each.
However, Labour's share of the vote was down 6%.
Harriet Harman, the Labour deputy leader, described tonight's results as "dismal" for the party, which was pushed into fifth place in the South East with half the votes counted.
Official EU projections indicated that the centre-right parties would emerge as the largest grouping in the European parliament.
Hours before the crucial Euro results were due to be announced, Brown's hopes of survival suffered a further setback when the former lord chancellor, Lord Falconer, became the most senior figure yet to call for a leadership contest.
The peer – once Tony Blair's flatmate – warned that potential candidates were waiting in the wings, ready to mount a challenge, if Brown was not prepared to stand down as prime minister.
Meanwhile, Tessa Jowell became the first member of the cabinet to speculate openly that Brown could be prepared to step aside if he believed he had become an "obstacle" to Labour winning the next general election.
If Labour were to end up coming fourth behind the Liberal Democrats, it could be the catalyst for plotters behind the so-called "peasants' revolt" to show their hand when MPs return to Westminster tomorrow.
Brown sought to rally support with a televised address to a hastily arranged gathering of sympathetic Labour party activists in east London earlier today.
He said the public would not understand if the government gave up at a time when it was faced with tackling the recession and cleaning up parliament.
"What would they think of us if ever we walked away from them at a time of need? We are sticking with them," he said.
"We have a purpose, we have a mission, we have a task ahead. We are going to get on with that task of building a better Britain."
Falconer's call for a leadership contest was swiftly rejected by the newly promoted home secretary, Alan Johnson, who is widely regarded as the most likely successor to Brown if the prime minister is ousted.
"I don't agree that regicide gives you a unified party," he told the Politics Show. "I think that Gordon Brown is the best man for the job."
Earlier, the business secretary, Lord Mandelson, cast doubt on the ability of the plotters to put up a credible candidate against Brown.
"It would require somebody to stand against him, somebody who is raising their standard and saying that they could do a better job ... we don't have that person," he said.
He told rebels to "stop taking shots" at the prime minister and warned that they faced the prospect of having to fight an immediate general election if Brown went.
However, Nick Raynsford, another former minister who has been calling on Brown to stand down, said the party could not carry on as it was.
The flashpoint could come as soon as tomorrow's weekly meeting of the parliamentary Labour party at Westminster, when Brown is expected to address his backbench MPs.
It will be followed almost immediately afterwards by a debate on Labour's future, addressed by the former Europe minister Caroline Flint – who resigned from the government on Friday – and the arch-Blairite Stephen Byers.
{Promotion Removed}