UKIP looked set to top the British European elections tonight as anti-EU sentiment swept the continent.
Politicians from the three main UK parties conceded they had been punished by voters fed up with the status quo.
With results still coming in, Ukip leader Nigel Farage said his party had humilitated Labour and the Conservatives by pushing them into second and third place.
And he predicted "a much bigger impact on the member states" as a result of a growth in anti-EU voting across Europe.
Talking about the political fallout from the Ukip surge, he said: "In the UK we may see a party leader forced out and another [Ed Miliband] may be forced to change his position on a referendum."
Emboldened by the party's success, Mr Farage said: "Our target strategy for [the General Election] next year has just become a lot more serious. Whose to say what Ukip can or cannot achieve in a General Election. It's not beyond the bounds of possibility that we might hold the balance of power."
Foreign Secretary William Hague said voters had sent the EU a clear sign. "There's a message coming across of disillusionment with Europe and the EU has got to hear that message loud and clear," he said.
Mr Hague claimed Ukip had offered voters a "free hit - a vote that doesn't have the consequence of putting the wrong Government in".
The Foreign Secretary said the EU should be concerned about the rising of Far Right parties, like the French National Front.
Labour's deputy leader Harriet Harman said: "People have said they are voting Ukip even if they are a Labour supporter in order to give us a shake-up."
Eurosceptic Conservative MPs said the results from across Europe proved their point.
Harwich and Essex MP Bernard Jenkin wrote on Twitter: "Some of us who opposed Maastricht 20 years ago predicted it would lead to the rise of the right in the EU: and here we are."
Douglas Carswell, the Clacton MP, said: "So maybe those of us who sometimes banged on about Europe were on to something?"
The Liberal Democrats appeared to be the biggest victims of the "earthquake" in British politics caused by Ukip, with Nick Clegg's party struggling to hold on to any of its MEPs.
Mr Clegg gambled by taking on Nigel Farage in head-to-head debates ahead of the European elections and highlighted his support for the Brussels project by casting the Lib Dems as the "party of in".
But the Lib Dems lost seats across England as the main parties conceded defeat in the face of a Ukip surge and the Deputy Prime Minister will face further questions about his leadership.
Party president Tim Farron, seen as a possible successor to Mr Clegg, said the Deputy Prime Minister should not face a leadership challenge despite a "staggeringly disappointing" European election result.
The Lib Dems had "paid the price" for the decision to fight a strongly pro-European campaign, he said, but he told Sky News that Mr Clegg should be praised for having the backbone to take an unpopular position over the EU and confront Ukip's "threat to British cultural values".
The night was a disaster for the BNP, however. The party was wiped out with leader Nick Griffin set to lose his seat.
In France, the far-Right National Front caused a sensation as it topped the polls for the first time in its 40-year history.
It was the same story in Greece where the anti-Europe Syriza party came top and the extremist Golden Dawn party looked on course to win at least one seat.
The anti-Islam Danish People’s Partyand the Italian Eurosceptic Five Star movement (M5S) also did well.

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