Nigel Farage's Brexit Party is tipped to win the most UK seats in the European Parliament elections, with establishment parties forecast to lose their majority across the European Union.
Official exit polls are revealing a tough night for establishment parties across the continent, while voter turnout is at 51 per cent according to the EU Parliament - its highest since 1994.
In France, Marine Le Pen's far-right National Rally party will take top spot, with 23.2 per cent of the vote against Macron's centrist grouping on 21.9 per cent according to polls.
In Germany, Angela Merkel's Christian Democratic Union and the centre-left Social Democratic Union could be on course for their worst result at European elections.
The CDU are polling just 28 per cent of the vote, down from 38 per cent in 2014 - a result which would be a significant blow to Mrs Merkel.
It looks to be an even worse night for the SPD who are polling at just 15.5 per cent, and who could leapfrogged into second place by the Green Party on 22 per cent.
Votes are being counted across 28 EU countrieswith polls closing at 10pm, and official provisional results for the UK are expected shortly after.
By the early hours of Monday, we should have results from the majority of UK regions, allowing us to see just how seismic a political shift has taken place.
Pre-election polls indicated that the two large establishment blocs in the European Parliament, which comprise a host of allied parties from each country, would lose seats under a tide of both populist and liberal support.
While the centre-Right European Peoples' Party (EPP) and centre-Left Socialists & Democrats (S&D) are likely to remain the largest parliamentary groups, forecasts indicated they would collectively lose dozens of seats.
UK polls show the Brexit Party winning the most seats
In the UK, Nigel Farage's Brexit Party is expected to gain the most seats, ahead of the two major parties. This would mark a repeat of his success with Ukip in the 2014 European election.
Labour and the Conservatives were both polling at less than 20 per cent in the run-up to the vote, with some experts predicting that Theresa May's Tories could fall to their lowest vote share in a national election since they formed in 1834.
The Lib Dems, Greens and Change UK - all backers of a second referendum - collectively had support of 30 per cent of the public in pre-election polls on election day, against no-dealers Ukip and the Brexit Party's collective 36 per cent.
Polling shows that revoking Article 50 and a no-deal Brexit - the two extremes of the Europe debate - are currently the most popular outcomes among the public, and parties were fighting to claim this political ground ahead of the vote.
The lack of a Remain alliance - with the Lib Dems, Greens and Change UK all competing and splitting the pro-European vote - makes their job of converting votes into seats even harder.
An analysis of regional polling data showed that the Greens, Lib Dems and Change UK would stand to win an additional 10 MEPs at the EU elections if they stood as a single anti-Brexit entity, giving them a total of 18 seats.
In 2014, Nigel Farage's Ukip topped the polls, securing 27.5 per cent of the national vote and 24 MEPs. Most of these MEPs have now defected to other parties now, including the Brexit Party.
Europe-wide establishment parties expected to lose their majority
At a continent level, the European Union's established centre-Left and centre-Right blocs were forecast to lose their combined majority in the elections.
The pre-election polls indicated that the two large pan-European blocs, the EPP and the S&D, will lose seats under a tide of both populist and liberal support.
The loss of their combined majority is likely due to the rise of the liberal Alliance of Liberals and Democrats for Europe (ALDE) and eurosceptic Europe of Nations and Freedom (ENF).
The latter of these blocs, the populist-Right ENF, is poised to morph into a new group called European Alliance of People and Nations after the election, under Italian Deputy Prime Minister Matteo Salvini.
The ALDE and ENF made the largest gains in the election, leading experts to warn that the new Parliament could be more fractious with majorities harder to come by.