Berlusconi is facing strong opposition in the Senate

The law would allow Mr Berlusconi to retain control of three private TV channels and add radio stations and pay-per-view television to his current interests.

The Senate is expected to vote on the law on 17 July after considering more than 5,000 amendments brought by the opposition, which has described it as the "mother of all conflicts of interest".

We are fighting to have that minimum of plurality which the president was demanding a year ago and which today is absolutely not guaranteed Centrist senator Willer Bordon

The debate is taking place against a backdrop of a new row with Germany, following insulting remarks about German tourists made by a junior minister.

That row followed Mr Berlusconi's outburst in the European Parliament last week, when he compared a German MEP to a concentration camp guard.

The prime minister's critics point to what they say was favourable TV coverage of last week's furore as evidence that Mr Berlusconi's influence over Italy's media is dangerous.

Success guaranteed

The legislation being discussed in the Senate would relax limits on how much of the media any one company could own.

Under current rules, Mr Berlusconi would be required to limit the number of private TV channels he owns to two.

The truth is that the Left has no interest in a good law being passed in this sector Renato Schifani Senate government whip

The prime minister currently controls about 90% of Italian television through his family's ownership of commercial channels and his influence as prime minister over the state broadcaster Rai.

The BBC's Jonathan Charles in Rome says Mr Berlusconi's majority in both houses of parliament virtually guarantees that he will get his way.

But left-wing and some centrist senators are determined to slow the process down.

"We are fighting to have that minimum of plurality which the president [Carlo Azeglio Ciampi] was demanding a year ago and which today is absolutely not guaranteed," Senator Willer Bordon of the centrist Daisy party told Italian TV on Tuesday.

"Everyone is saying this with the exception of Berlusconi, who is defending his own interests."

However, a Senate whip for Mr Berlusconi's Forza Italia party, Renato Schifani, said the government was protecting plurality of information.

"The truth is that the Left has no interest in a good law being passed in this sector," he said.

Parliament has already passed several bills which critics say are tailor-made to aid Mr Berlusconi's business interests and to bail him out of his legal entanglements in the courts where he faces corruption charges.