LONDON — Members of the European political elite expressed alarm Monday over the strong showing in European Parliament elections by nationalist and anti-immigrant parties skeptical about European integration, a development described by the French prime minister as an "earthquake."
In France, Britain, and elsewhere, anti-immigrant parties opposed to the influence of the European Union emerged in the lead. In France, the National Front won 26 percent of the vote to defeat both the governing Socialists and the Union for a Popular Movement, the center-right party of former president Nicolas Sarkozy.
In Britain, the triumph of the UK Independence Party, or UKIP, which won 28 percent of the vote, represented the first time since 1910 that a nationwide vote had not been won by either the Conservatives or Labor.
"The people's army of UKIP have spoken tonight and delivered just about the most extraordinary result that has been seen in British politics for 100 years," said Nigel Farage, UKIP's leader.
Official results released overnight showed that populist parties strongly opposed to the European Union also trounced establishment forces in Denmark and Greece and did well in Austria and Sweden. The results, a stark challenge to champions of greater European integration, left mainstream political leaders stunned.
The radical left-wing Syriza coalition in Greece beat the party of Prime Minister Antonis Samaras, while Golden Dawn, a neo-Nazi outfit that the Greek authorities have tried in vain to outlaw, also picked up seats, bringing Holocaust-deniers and belligerent xenophobes into the European Parliament.
With the political landscape redrawn across Europe, some politicians, notably Nick Clegg, the British deputy prime minister and leader of the Liberal Democrats, the junior coalition partner, faced calls from their own party members to quit. The Liberal Democrats finished fifth in Britain and lost nearly all their seats at the European Parliament.
In Spain, the two main parties failed for the first time to get a combined 50 percent of the votes. Such was the upheaval that Alfredo Pérez Rubalcaba, the leader of the Socialist Party, said Monday he would step down after failing to capitalize on Spain's economic woes and record unemployment to beat the governing Popular Party.
Traditional parties sought to depict the ballot as a protest vote inspired by deep alienation among voters repelled by what they consider to be out-of-touch political elites at home and an arrogant European Union bureaucracy spreading its influence with no democratic mandate.