A court in Milan has challenged a new law which gives Prime Minister Silvio Berlusconi immunity from prosecution.
In the spotlight: Italy takes over the EU presidency EU on Tuesday
The court, which is trying Mr Berlusconi on charges of bribing judges, said the law may be illegal and asked the Constitutional Court to investigate.
Lawyer's for Mr Berlusconi denounced the court's decision as "political".
Mr Berlusconi is accused of trying to bribe judges to stop a business rival taking over state-owned food group SME in the 1980s.
The trial is seen as a potential embarrassment for the prime minister as Italy takes over the presidency of the European Union on Tuesday.
There is a cancer in Italy that we must cure - the
politicisation of the bench
The Milan court suspended the case, in accordance with the new law, until the higher court rules.
Correspondents say this could take several months.
Earlier on Monday, Mr Berlusconi repeated accusations of bias against the media and judiciary.
"Eighty-five percent of the press is left-wing, and the judges
are worse. There is a cancer in Italy that we must cure - the
politicisation of the bench," he told French Europe 1 radio.
Last week, a prosecutor at the Milan court described the law as "openly anti-constitutional and opposed to the cardinal principles of our constitution".
Under the law, magistrates can investigate allegations against the five top figures, but cannot bring them to trial.
As well as the prime minister, the law also covers the president, the speakers in both houses of parliament and the president of Italy's constitutional court.
Mr Berlusconi is Italy's richest man, heading a multi-billion-euro empire that encompasses broadcasting, banking, publishing and the AC Milan football club.