The defence, who denied there had been an attempt at obstruction, had called the former couple to certify that the dinners held by Berlusconi in 2010 were not the orgies of debauchery described in telephone conversations by several of the young female participants.

Berlusconi is accused of having sex for money with Moroccan exotic dancer Karima El-Mahroug, better known as "Ruby the Heart Stealer", when she was 17.

He is also charged with abusing his position as prime minister by telling police to release her when she was arrested for petty theft in May 2010.

That year, Mahroug said under questioning that she had seen Clooney and Canalis attend a party at Berlusconi's home, a claim both have denied, with Clooney telling magazine last year that he had only met the former premier once to seek help in the Darfur conflict.

Boccassini said yesterday that the defence had not contacted Canalis, a showgirl who lives in the United States, in time. As for Clooney, "does it seem possible to you that you can establish contact with the American actor in less than a week?" she asked the defence.

Niccolo Ghedini, from Berlusconi's defence team, said there had been no attempt at obstruction. "There are already 10 or 11 witnesses today," he said. "This trial is moving ahead particularly rapidly at the rate of a hearing a week."

Ghedini said he wanted to work in the "fairest and most transparent manner possible" in respect of the court.

The court has approved a total of 78 witnesses for the defence and 136 for the prosecution, including 32 young women who are said to have participated in the Berlusconi parties.