Nigel Farage claimed to have pulled off the "most extraordinary result in British politics for 100 years" as Ukip surged to the top of the European polls in a contest which will leave the leaders of Westminster's main parties counting the cost.
With all English and Welsh regions now declared, the number of MEPs now stands at:
- Ukip 23 MEPs +10 change (29.07% vote share)
- Labour 18 +7 (25.4%)
- Conservatives 18 -7 (23.9%)
- Green 3 +1 (7.9%)
- Liberal Democrats 1 -9 (6.9%)
- Plaid Cymru 1 = (0.7%)
The final result in Scotland will be announced later, but with only the Western Isles left to declare it appears the SNP and Labour will retain their two Scottish MEPs, with the Scottish Tories also keeping their European representative.
But the Liberal Democrats appear to have lost their one MEP, with that seat going to Mr Farage's party, giving them a first foothold in Scotland.
ITV News Political Editor Tom Bradby said that considering the performance of the far-right National Front in France and Ukip in the UK, "it is possible that Europe's leaders might finally give consideration to some substantial reform, particularly on issues like immigration."
Ukip's opponents will scrutinise the stunning performance of Mr Farage's "people's army" for signs that the results are skewed by protest votes which may change at next year's general election.
But in his acceptance speech after topping the poll in the South East, Mr Farage promised: "You have not heard the last of us."
Speaking to ITV News deputy political editor Chris Ship after the result, Mr Farage hailed a "massive result...right across the United Kingdom" and promised a "breakthrough coming tomorrow in Scotland."
He added that he would make the decision as to where to stand for a Westminster seat "before the summer recess" and confirmed it would be a constituency in the South East region.
The Liberal Democrats were the night's biggest losers as Nick Clegg paid the price for his gamble to position the party as the natural opponents to Ukip's Euroscepticism.
In a humiliating set of results, the party lost all but one of the 11 MEPs it went into the contest with and was relegated to fifth place behind the Greens.
In Wales the Lib Dems lost their deposit and finished in sixth position.