German socialist Martin Schulz, tipped to become European Parliament president on Tuesday, is a former librarian with a fiery temperament who made his name in an altercation with Silvio Berlusconi.

The then Italian premier sparked a diplomatic spat between Rome and Berlin in 2003 when he said during a parliament debate that Schulz would be perfect in the film role of a "kapo", a prisoner who worked for the Nazis in concentration camps.

The bearded, bespectacled German politician had vexed the boisterous billionaire by raising questions over alleged conflicts of interest between Berlusconi's political role and his media empire.

Unknown in Europe and even in his home country before his run-in with Berlusconi, Schulz took the helm of the Socialists and Democrats (S&D) bloc in the European Parliament a year later.

Set to succeed former Polish prime minister Jerzy Buzek, a conservative, at the helm of the parliament, Schulz can express himself in French and English with ease, an asset in a 27-nation assembly of 736 lawmakers.

"His is a staunch European," the co-leader of the Green group, Franco-German lawmaker Daniel Cohn-Bendit, told AFP.

Schulz, a member of the European Parliament since 1994, will be able to defend the role of EU institutions "in the face of attempts to renationalise" policymaking in the 27-nation bloc, Cohn-Bendit said.

Under a deal between the conservative European People's Party and the S&D, the parliament's first and second blocs, to rotate the presidency, the EPP will back Schulz in Tuesday's election.

A member of Germany's centre-left Social Democrats since the age of 18, Schulz has vowed to "fight" EU states to defend the powers of the Parliament and reduce the union's "democratic deficit".

He is credited with having helped to ensure that the new job of EU foreign and security policy chief be given to a politician from the left in 2009, a post since held by British Labour politician Catherine Ashton.

The 56-year-old German does not smoke or drink. "He has a very strict lifestyle," a member of his entourage said.

On camera, he is an outspoken voice in the parliament who has denounced "casino capitalism" or Franco-German domination of European policymaking.

He has ruffled feathers with many politicians, including French socialists, whom he compared to pigeons.

"When they are up, they crap on your face, and when they are down they eat from your hand," Schulz once told reporters.

Eurosceptics and far-right politicians despise him.

"Mr. Schulz has Lenin's face and speaks like Hitler," French far-right leader Jean-Marie Le Pen said after Schulz successfully blocked him from presiding over the parliament's inaugural session in July 2009 as the assembly's oldest member.

In 2010, Godfrey Bloom, a member of the UK Independence Party, was briefly ejected from parliament for uttering a Nazi slogan and calling Schulz an "undemocratic fascist" after the German politician criticised Britain.

In his bid to become European Parliament president, Schulz "did everything to offend as little as possible", said a European official.

Schulz is believed to be eyeing the job of European Commission president, the job held by former Portuguese conservative prime minister Jose Manuel Barroso, with whom he often clashes.

"For that to happen, he will have to restrain himself and not anger European leaders," said another EU official.