Jean-Claude Juncker declared victory in the European elections on Sunday, and staked his claim as the first man in line to claim the European Commission presidency, the EU Observer said.

With partial results and exit polls suggesting that the centre-right EPP had claimed 212 seats in the European Parliament to 185 Socialists, Juncker, the former prime minister of Luxembourg, was presented as the next president of the EU executive by jubilant party supporters.

"As lead candidate of the largest party, I have won the election," he told reporters in the Parliament hemicycle. "The EPP has got a clear lead, a clear victory."

He also insisted that he would not stand aside for another EPP candidate and issued a warning to EU leaders not to "ignore" the results by opting to "select the President in corridors".

Leaders of the Parliament's political groups will meet on Tuesday morning to begin the process of allowing a candidate to build a majority in the EU assembly. EU leaders will then gather in Brussels on Tuesday evening to have their first discussions following the elections.

Following nomination by EU leaders, a successful candidate will need the support of at least 376 deputies in the 751-member Parliament.

But Juncker stated that he would seek to build a broad majority of pro-European forces, including the Green and Liberal groups as well as the Socialists.

"I will not be on my knees with the Socialist party … but even party No 1 has to make compromises," he said, adding that he had "a lot of sympathy with Greens and friends in the Liberal group".

But Socialist candidate Martin Schulz refused to concede defeat and insisted that he, as well as Juncker, would try to form a majority.

"It's much too early to discuss who will be the supporter of who," commented Schulz. He added that the Socialist group would expect any candidate to sign up to a policy platform based on tackling youth unemployment, fighting tax fraud and tax evasion, and more regulation of the banking sector.

"Without the Social Democrat group no majority is possible," he said. "We are prepared to negotiate and therefore I am looking with interest to the next hours and days."

For his part, Liberal leader Guy Verhofstadt, whose group is set to remain as the third largest force in the Parliament with around 70 seats, refused to call time on his own bid for the Commission presidency.

"What we have agreed is that the first group gets first chance to form a majority, followed by the second group, and possibly the third," he said

"A stable majority is more than 400 MEPs. The two main groups do not have this. Any majority will need the third party," added Verhofstadt.

But with the projected results indicating a surprisingly large margin of victory between the EPP and the Socialists, Juncker is in a clear pole-position amongst the five 'Spitzencandidaten' to become the next head of the EU executive.