Gordon Brown's political survival hung in the balance today as Labour suffered a devastating rout in the European elections.

The party was beaten into third place by the UK Independence Party (Ukip) in the popular vote while the far right British National Party achieved a major breakthrough by gaining its first Euro seats.

The scale of the defeat could be the catalyst for rebel Labour backbenchers manoeuvring to oust Mr Brown to come out into the open and launch a direct leadership challenge.

With almost all the results from across the UK in, Labour had managed just 15.4% of the popular vote to Ukip's 17.5%.

The Tories had 28.3% while the Liberal Democrats were in fourth with 14%.

Despite the victories in the North West and Yorkshire, the BNP had a lower share of the vote than the Greens, with 6.6% to their 8.8%.

Labour lost five seats to leave them with just 11, two fewer than Ukip with 13 and 13 behind the Conservative tally of 24.

Deputy leader Harriet Harman admitted that they had been a "very dismal" set of results for the party.

She sought to deflect attention from the Prime Minister, putting the blame for Labour's poor performance on the row over MPs' expenses which, she said, had hit the party particularly hard.

"Our supporters are absolutely furious with us about expenses," she said. "They expect us to have higher standards than the Tories."

However Labour MPs returning to Westminster today will be weighing up whether they now need to ditch Mr Brown if they are going to stand any chance at the next general election.

The results will set the scene for a tense meeting this evening of the Parliamentary Labour Party where the Prime Minister is expected to address his shell-shocked backbenchers.

The former Lord Chancellor, Lord Falconer - the most senior figure so far to break cover - repeated his call for a new leader to re-unify the party.

"I think unity will only come with a leader that the mainstream votes for," he said.

There will be particular dismay that the party has fallen so far that it opened the door for the BNP to take seats in Yorkshire and the Humber and in the North West where the party's leader Nick Griffin was elected.

Health Secretary Andy Burnham said that it was "deeply uncomfortable" to see the BNP polling in such large numbers.

He said that they had been the beneficiaries of an "anti-politics mood" which had hit all the main parties in the wake of the MPs' expenses scandal.

"It is a sad moment in British politics," he said.

"The BNP is like the ultimate protest vote. It is how to deliver the establishment a two-fingered salute. I think largely it is a comment on Westminster politics."

Conservative Party chairman Eric Pickles said the BNP had been able to make its breakthrough because of Labour weakness.

"What has essentially happened is that there has been a retreat particularly by Labour but we haven't been able to fill that particular vacuum," he said.

"What seems to have happened is that Labour voters have been squeezed beyond what we thought was possible - and the BNP has been the beneficiary of that.

"I'm not pleased about that."

Mr Griffin said that Labour was paying the price for turning the country into "a crime-ridden slum with no industry left" and said that he was determined to build on their success.

"The party is going to go on and grow very rapidly. We're going to be major contenders in a number of places in the next general election and the next wave of council elections," he said.

One of the most dramatic results of the night came in Wales where Labour was beaten into second place for the first time in any election since 1918.

Labour was also heading for second place in Scotland behind the Scottish National Party, while in two English regions - the South East and the South West - it was beaten into fifth place behind the Greens.

A jubilant Ukip leader Nigel Farage said that the result showed that his party's unexpected third place in the last European elections was no fluke.

"This time we have come second in a major national election. That is a hell of an achievement especially given that over the last three or four weeks we have not really had a proper debate about the European question," he said.

Senior Liberal Democrat Simon Hughes said that his party had held its ground while there had been a "significant loss" for Labour.