Panic has set into Labour and the Conservatives after Nigel Farage’s dramatic Euro-poll win, which sparked fresh demands for referendums on Brexit and independence for Scotland.

The jubilant leader of the Brexit Party warned the two established parties that if Brexit did not happen, then it would “stun” them again by laying siege to constituencies the length and breadth of Britain in a general election. Mr Farage even demanded a role for his party in the UK Government’s talks with Brussels.

"We're not just here to leave the European Union but to try and fundamentally change the shape of British politics, bring it into the 21st century and get a Parliament that better reflects the country," declared the MEP.

Theresa May’s Conservatives suffered their worst electoral drubbing since 1832, losing 15 seats and winning four. They were warned by Jeremy Hunt, the Foreign Secretary, the party now faced an “existential risk” and had to deliver Brexit.

The Prime Minister said it had been a "very disappointing night" for the Conservatives.

"Some excellent MEPs have lost their seats, some excellent candidates missed out. But Labour have also suffered big losses.

"It shows the importance of finding a Brexit deal and I sincerely hope these results focus minds in Parliament," she added.

The Farage victory caused Tory contenders, wanting to succeed her in No 10, to emphasise their willingness to take Britain out of the EU, deal or no deal, in order to blunt the Brexit Party’s electoral threat.

Esther McVey, the former Work and Pensions Secretary, one of nine candidates vying for the Conservative crown, said: "The message from our voters is clear: we must leave the EU on October 31 with a clean break; nothing else will wash now.

"People saying we need a Brexit policy to bring people together are misreading the situation. That is clearly not possible," she insisted.

Sajid Javid, the Home Secretary, announced his leadership candidacy, saying: "First and foremost, we must deliver Brexit."

Labour also suffered a drubbing, seeing its MEPs halved in number to 10. It polled just 14 per cent, a "disastrous" performance, according to deputy leader Tom Watson, blamed on the party’s equivocal policy on Brexit.

It also came a humiliating fifth in Scotland, losing its two MEPs, and having polled less than 10 per cent, down from 26 per cent in 2014. The poor showing prompted MPs Ian Murray and Martin Whitfield to warn if the party failed to listen and learn from the result, then it would “never recover”.

Their Labour colleague David Martin - who has been the UK's longest-serving MEP having first been elected in 1984 – tweeted: “We lost not because of lack of effort but lack of clear message."

Last night, facing intense pressure from senior colleagues, Jeremy Corbyn shifted policy to say Labour was now “ready to support a public vote on any deal”.

Nicola Sturgeon hailed an “historic and spectacular” result for the SNP, which won three of the six Scottish MEP seats, having polled 38 per cent of the vote, up five points on 1994. The Brexit Party secured second place in Scotland and won one seat as did the Tories and Liberal Democrats.

While on a trip to Dublin, the First Minister announced that legislation for a second Scottish independence referendum would be tabled this week and called for a new poll on Scotland's future to take place in the second half of next year. But Westminster is the constitutional authority and the UK Government has set its face against facilitating another poll before the 2022 General Election.

Ms Sturgeon insisted: “Suddenly, this idea of being a small independent country in the European Union, we only have to look at Ireland to see the benefits of that and many people are having their eyes opened."

Ruth Davidson for the Scottish Conservatives said it had been clear her party was set to get a kicking in the Euro-poll.

“The arrival of the Brexit Party demonstrates the clear frustration of the Scottish electorate that Brexit still isn’t sorted,” she declared.

The Edinburgh MSP committed to “redoubling” her efforts to get rid of the Nationalist Government, adding: “Dividing the pro-Union vote only benefits one party: the SNP.”

The Lib Dems, following on from their good performance in the local elections in England earlier this month, had another successful night, gaining 15 seats.

Jo Swinson, the deputy leader, hailed the result, saying the party had brought people together. “To be able to get Michael Heseltine and Alistair Campbell united in the voting booth is no mean feat," she said.

Within the next 72 hours, Ms Swinson, her party’s deputy leader who represents East Dunbartonshire, is expected to announce her bid to succeed Sir Vince Cable as Lib Dem leader. Hustings begin on Friday.

The Green Party also had a successful night, winning four MEP seats to bring its total to seven. It finished above the Conservatives for the first time in a national election.

Sian Berry, the Greens’ co-leader, said: "There is clear evidence from this of strong support for the UK remaining in the European Union but also for tackling the causes of Brexit: the massive damage done to so many communities by austerity; tax-dodging and diminution of workers' rights."

The scale of the Tory disaster was underlined by its nine per cent vote share; in fifth place across the UK behind the Brexit Party on 32 per cent, the Lib Dems on 21, Labour on 15 and the Greens on 12.

Voter turnout in Great Britain was the second highest for an EU election, but still low at 36.7 per cent.

Change UK, the new centrist pro-Remain party, failed to make a mark. There is now talk at Westminster of a possible merger with the Lib Dems.

Ukip lost all its 24 MEPs in the wake of the rise of Mr Farage’s Brexit Party. Its leader Gerard Batten lost his seat in London, which he had held since 2004.

In Northern Ireland, the Democratic Unionists, Sinn Fein and the Alliance Party all picked up one seat.