Eurosceptics score major win in Britain

UKIP had been expecting to do well in the election but the extent of its win was surprising, as it came second with 16.5 percent and obtained 13 seats, one more than in the last parliament.

The Labour party of prime minister Gordon Brown, badly hit by the recent scandal over MPs' abuses of the expenses system, only came third at 15.7 percent and lost five of its 18 MEP seats. British media note that it was Labour's worst score since World War II.

UKIP leader Nigel Farage said his party's score was a "hell of an achievement" and called on the prime minister to resign.

"He has been beaten by a party that he mocked and derided as being on the fringes - so if we have beaten him, he has got to go," Mr Farage said.

For his part, Conservative leader David Cameron said he was "delighted" with his party's result and reiterated his calls for early general elections.

"We topped the poll, we increased our share of the vote, increased our number of MEPs, we won in almost every part of the country and had some staggering results," he told the BBC.

"Obviously the next election should be a general election… the longer we put off this election, the greater the anger [of the British people] will be," he added.

Lisbon referendum?

The prospect of a snap general election and a potential Tory victory spells turbulence for Brussels, with its leader David Cameron having promised to hold a referendum on the Lisbon treaty if he comes in power before it is ratified in all EU states, as well as to call for the EU to return powers to London.

"We have pledged that if the constitution [the Lisbon Treaty] is not in force in the event of the election of a Conservative government this year or next, we will hold a referendum on it, urge a No vote, and – if successful – reverse Britain's ratification," Mr Cameron said in April.

He later tabled a bill under which a UK referendum would be held together with Ireland's second vote on the treaty, expected to take place in the autumn.

The UK parliament has already ratified the Lisbon Treaty, but as Britain has no written constitution, the Tory leader would in fact not be breaching any rules if he proceeded to reversing the ratification, British liberal MEP Graham Watson explained on Monday.

"Nothing sets legal limits on what a government can or cannot do [in the UK]," Mr Watson told a news conference in Brussels.

He added he was "worried" by Mr Cameron's intentions to reopen the Lisbon debate in Britain and on the consequences this would have on the UK's place within the EU.

"I am very worried by the position adopted by David Cameron on the Lisbon Treaty. It's almost incredible, unbelievable for a country which was a full part of the negotiations for this treaty… This party is now trying to reopen the debate," he said.

"I would hate to think what would be the impact on the relations [between the UK and the EU]… if a government would come in office and rip out a treaty that its predecessors signed and ratified," he added.

'Depressing day' for British politics

Meanwhile, the far-right British National Party obtained 6.2 percent of the votes and secured two seats in the European parliament for the first time in its history.

The BNP seats will be taken by the party leader Nick Griffin and another candidate, Andrew Brons.

The BNP result prompted regret among both Labour and Tory politicians.

"I think it's a terrible thing that we've now got representing Britain in the European parliament a party that is a racist party, a party that doesn't believe black people should even be allowed to join this party," Labour deputy leader Harriet Harman told the BBC.

For his part, Mr Cameron said the result was "desperately depressing," because the BNP were "an appalling bunch of people."

"It's obviously a depressing day for all of us," he said.