Mr Giuffre, who turned state's witness after his arrest in April, said Mafia bosses had visited Mr Berlusconi's villa near Milan, purportedly to see a person who worked there, media reports say.

Dell'Utri was a person very close to Cosa Nostra and at the same time he was an excellent reference for Berlusconi, and was therefore known as a serious and trustworthy person Antonino Giuffre

Mr Giuffre, who spoke over a video link from a secret location, is testifying in the trial of Marcello Dell'Utri, a senator in Mr Berlusconi's Forza Italia Party.

Mr Dell'Utri is accused of using an advertising business - part of Berlusconi's Fininvest business empire - to launder Mafia money.

The highest-ranking member of the Cosa Nostra to co-operate with investigators, Mr Giuffre said Mr Berlusconi used to be in touch with Stefano Bontade, a top Mafia boss, who visited Mr Berlusconi's villa in Arcore.

Mr Giuffre added that the mobster's contact at Mr Berlusconi's villa was the late Vittorio Mangano, a convicted Mafioso who used to be a stable manager there.

"When Vittorio Mangano got the job in the Arcore villa, boss Stefano Bontade and some of his close aides used to meet Berlusconi using visits to Mangano as an excuse," Mr Giuffre said.

He told the Palermo court that despite the prime minister's assertions to the contrary, Mr Mangano's Mafia identity was known when he was hired at the villa.

"Berlusconi was afraid of kidnappings, so Dell'Utri introduced him to Mangano," Mr Giuffre said in his deposition to state prosecutors ahead of the senator's trial.

Mr Giuffre will also testify in former PM Andreotti's appeal trial

Mr Giuffre was formerly the right-hand man for Bernardo Provenzano, the Cosa Nostra head who has been on the run for more than 30 years.

"Dell'Utri was a person very close to Cosa Nostra and at the same time he was an excellent reference for Berlusconi, and was therefore known as a serious and trustworthy person," Mr Giuffre said, speaking with his back to the video camera.

Mr Dell'Utri denies the charges, which are largely based on the evidence of other Mafia turncoats.

On Tuesday, he said the government's anti-Mafia record proved there was no tie between Mr Berlusconi and Cosa Nostra.

Mr Berlusconi himself was also questioned during the trial, but he exercised his right to silence during the special court session held in Rome in November.

'Political links'

According to Mr Giuffre, the relationship between Mr Dell'Utri and the Mafia gained importance in 1993 after the collapse of the Christian Democrat Party amid widespread corruption trials.

At that time, Mr Berlusconi was putting together his Forza Italia Party to fill the political vacuum.

"Cosa Nostra was interested in making contact with the upper echelon of this movement," Mr Giuffre said.

Mr Giuffre is also expected to testify at the appeal trial of Giulio Andreotti, Italy's seven-time prime minister who has been accused of association with the Mafia.