Nigel Farage has unleashed his much-promised political earthquake across British politics as Ukip stormed to victory in the European elections, performing powerfully across the country.

The Eurosceptic party's victory marked the first time in modern history that neither Labour nor the Conservatives have won a British national election.

In a stunning warning to the established political parties, Ukip was on course to win as much as 28% of the national poll. That is a near doubling of the 16.5% it secured in the last European elections in 2009, when it came second to the Tories with 13 seats.

Twenty years ago, in its first European election, Ukip managed 1% of the vote.

The Liberal Democrats suffered a near-total wipeout losing all but one of its 11 MEPs and placing serious pressure on Nick Clegg to justify his leadership of his party as its share of the national vote was 7 %.

Labour was predicting that when all the final results are assembled it will have polled 25.7% and the Tories 24.5%, but Labour was dependent on a very strong showing in the capital against the Conservatives to ensure it pushed the governing party into third place. The Green party will have come fourth.

Farage said the result justified the description of an earthquake because "never before in the history of British politics has a party seen to be an insurgent party ever topped the polls in a national election".

He claimed voters had "delivered about the most extraordinary result that has been seen in British politics for 100 years and I am proud to have led them to that." The Ukip leader predicted that as a consequence: "We may well see one party leader forced out of his position and another to reconsider his policy of opposition to a referendum on Europe, and David Cameron will have to take a much tougher negotiating stance. It is now not beyond the bounds of possibility that we hold the balance of power in another hung parliament."

The established parties at Westminster had been bracing themselves for a Ukip victory as opinion polls gave it a regular, if not wholly consistent or decisive lead over Labour. But the results also showed that Labour had underperformed against poll predictions, a result that will add to existing nervousness in the Labour party about the quality of Ed Miliband's leadership. The Labour belief that Ukip is causing disproportionate damage to the Conservatives looks increasingly dubious.

On the other side of the political fence, the influential Conservative MEP Daniel Hannan called for a pre-election pact with Ukip and demanding the Foreign Office toughen its renegotiation stance on Europe.

Ukip polled strongly across the country, except in some urban areas, and was expected to take a seat in Scotland, which formally declares on Monday. The SNP showed no increase in its share of the vote on 2009, but topped the poll in the nation.

The Tories, Labour and the Lib Dems will acknowledge that this is a powerful symbolic moment: a party that was founded in 1993 has pulled ahead of all the established parties, whose roots date back more than 100 years.

Ukip topped the poll in Doncaster, where Ed Miliband represents Labour and where Ukip plans to stage its autumn conference.

Ukip has topped the poll in six of the first nine declared region, with their strongest performance coming in the East Midlands, where their vote was up 16.5%

Labour topped the poll in Wales, the north-west of England, and the north-east of England allowing it to make five gains. With three regions to declare – London, Northern Ireland and Scotland – Ukip was due to have 22 MEPs, the Conservatives 16, Labour 14,and the Greens two.

As soon as the results came in, the scale of the devastation wreaked on the Lib Dems became clear –they suffered a near total wipe-out retaining only one of 11 MEPs.

In some regions its vote fell by more than 50% on 2009, and it had been beaten the Greens into fifth place, even in its former stronghold of the south-west. Graham Watson, the Liberal Democrat MEP in the region, lost his seat as its vote collapsed from 17% to 6%. The dire results emboldened those party activists calling for Clegg to quit, saying his name is toxic on the doorstep. Martin Tod, a member of the party's federal executive said "the response of the leadership in the face of this disaster is incredibly complacent". Tim Farron, the party president, said: "The results are as bad as I feared," He added: "Everything they had done was to get a result above nothing." He continued: "Nick Clegg had stood up to Ukip, and I would do it again. Britain is drifting to the exit door of the European Union."

Ed Davey, the Liberal Democrat energy secretary, admitted "it has been a difficult night for us". He accused Ed Miliband and David Cameron of failing to make the positive case for Europe in the campaign, and said "it had been right for Clegg to make that case, even if it had not worked yet". He dismissed the attempts to unseat Nick Clegg as not serious claiming the party was solidly behind the party leaders. Grant Shapps, the Conservative chairman, said this had been "a free hit election, and the general election will be anything but a free hit election", adding the only way to guarantee a referendum in 2017 is through a Conservative vote.

Martin Callanan, the former Tory leader in Europe, who was defeated in the north-east said "we must not get this out of proportion", arguing "European elections are not a good guide to what happens in the general election".

"My advice is to my party not to panic, to be calm and to be reflective. We must not obsess about Europe," he added.

In a worry for the Conservative plan to break the Ukip momentum in the Newark byelection in a fortnight, the Conservatives trailed Ukip in Newark in the European election by two points, a sign that Ukip could yet get its first MP shortly.

Roger Helmer, the Ukip byelection candidate who was re-elected as an MEP, said: "Britain is sending a hugely powerful message to the political classes tonight and I think Newark will relish the opportunity of reinforcing that message on Thursday week."

Labour said it had been expecting to lose for many weeks, and its vote was up 15.7 % on 2009 – a considerable jump – allowing the party to increase its current crop of 13 MEPs.

Labour was desperate to deflect any inquest towards David Cameron, with an insider claiming: "If the Tories come third, it will be the first time they have done so in a national election."

The Conservatives countered by saying that Labour's failure to win the European elections represented the first such failure by an opposition in 30 years.

The Tories said on Sunday night that votes confirmed the trend in some local elections with Labour failing to do well in general election target seats, such as Swindon, Stroud, Peterborough, South Pembrokeshire, Basildon, and North Warwickshire.

The last time that Labour or the Conservatives failed to win a national election was in December 1910 when Herbert Asquith won the highest number of seats, though not the largest number of votes, in the general election for the Liberal party. The Liberals were arguably on the winning side in the next general election in 1918 though in that "coupon election" the "coalition Conservatives" won 332 seats to 127 for the "coalition Liberals".

The main parties moved on Sunday to show they regarded the Ukip threat as serious. Iain Duncan Smith, the work and pensions secretary, announced that he aims to halve the amount of time – from six to three months – that EU migrants can claim benefits. Ed Miliband will move to show that he acknowledges the threat posed by Ukip on Tuesday when he visits the marginal constituency of Thurrock where his party lost control of the council after a strong showing by Ukip.