"The concerns of those who voted in protest or did not vote are best addressed through decisive political action for growth and jobs, and through a truly democratic debate."
The governing socialists of president François Hollande collapsed to 14 per cent and German Socialist MEP Martin Schulz said, "Pro-European parties have to take very seriously what is behind the vote."
"It's a bad day for the European Union, when a party with a racist, xenophobic and anti-Semitic programme gets 25 per cent of the vote" - Martin Schulz
Of the FN victory, he said, "It's a bad day for the European Union, when a party with a racist, xenophobic and anti-Semitic programme gets 25 per cent of the vote."
Belgian MEP Guy Verhofstadt, leader of the ALDE group, said, even after the vote, two-thirds of the MEPs would be "people who are in favour of the European Union".
French veteran MEP Alain Lamassoure, representing the opposition centre-Right UMP for the Paris area, said the result "will mean that France would disappear from Europe's political scene. This will be a tragedy for our country."
Parliament's S&D group leader Hannes Swoboda said, "This French result sends a clear warning bell to the rest of us."
More reaction came from Germany's foreign minister Frank-Walter Steinmeier, who labelled the FN victory a "severe signal" and voiced concern about the rise of Eurosceptic parties in European parliamentary elections.
"There is no doubt that many populist, Eurosceptic and even nationalistic parties are entering the European parliament," he warned.
Pawel Swidlicki, of the UK think tank Open Europe, said the effect of the FN result "shouldn’t be over-stated", adding, "These elections should serve as a major wake-up call. The EU elite should respond with sweeping reforms. Opting for even more centralisation will only further fuel the anti-EU vote."
It was not just the Eurosceptics that did well, with radical and nationalist anti-EU forces scoring major victories both on the far left and the hard left.
In Greece, Alexis Tsipras led the Syriza movement to a watershed victory for the left over the country's two traditional ruling parties - currently governing in coalition - the New Democracy conservatives and the Pasok social democrats. The neo-fascists of Golden Dawn took about 10 per cent.
George Tzogopoulos, of Greek think tank Eliamep, said, "The results show that people voted to punish the politicians of the status-quo."