Thousands of protesters are expected to march through Rome today to defend press freedom and demand answers from Silvio Berlusconi about his conduct.

Dario Fo, the Nobel prize-winning playwright, and Roberto Saviano, the author of the Mafia exposé Gomorrah, will lead the demonstration, which is expected to attract 300 coachloads of protesters from across Italy.

Mr Berlusconi has refused to answer questions, published every day for the past six months by La Repubblica newspaper, about his relationship with a teenage model. He is suing the publication for defamation.

What began as a sex scandal with allegations that women that were being paid to attend Mr Berlusconi’s private parties has blistered into a national debate over press freedom, polarising Italian politics.

Critics claim that their right to voice opinions against the Prime Minister, 73, is being dangerously undermined in print and, in particular, on television, which is dominated by Mr Berlusconi’s media empire.

Mr Berlusconi said in an interview this week: “This protest is a farce, which makes us look bad in the eyes of other countries. I believe this anti-Italianism at the core of many political positions and certain newspapers really does damage to the country.”

Roberto Natale, the president of the National Press Federation, which is organising the event, responded: “It will not be a farce but a serious demonstration.

“We notice a heavy cloud hanging over [the communication of] information: from the campaign against L’Avvenire to the Prime Minister’s appeal to businesses because they are not investing in advertising in his disastrous newspapers.” The editor of L’Avvenire newspaper was forced to resign after a campaign of character assassination by a Berlusconi-friendly editor.

Mr Berlusconi owns Mediaset, which controls Italy’s three main commercial channels, and, as Prime Minister, has direct influence over RAI, the public broadcaster. His Fininvest holding company also controls Arnoldo Mondadori Editore, the country’s biggest magazine publisher.

The protest comes after Carl Bernstein, the Pulitzer prize-winning American journalist who exposed Watergate, told an Italian talkshow that attempts to suppress discussion of allegations against Mr Berlusconi were absurd.

“The press has the legitimate right to ascertain if the evidence is true, in allegations against a head of state or a prime minister,” he said. “That was the case with Monica Lewinksy and Clinton, and is the case regarding Mr Berlusconi today.

“There is an absurd, almost unprecedented situation in a democracy, where the Prime Minister tries to suppress what’s left of the free press by restraining publication and broadcasts about his own conduct.”

The Prime Minister’s behaviour “recalls soviet Stalinism and is not worthy of a great Western democracy or a leader who strives to be involved with international affairs”.

Mr Bernstein was speaking on Annozero, a current affairs talkshow, which this week became the lightning rod for the press freedom debate after it broadcast the only television interview with the prostitute at the centre of the sex scandal, Patrizia D'Addario.

Il Giornale, a newspaper part-owned by Mr Berlusconi’s brother, urged Italians to stop paying their television licence fee to punish RAI for airing the interview.

La Repubblica says that it has 450,000 signatures in support of the press freedom campaign, including 11 Nobel prizewinners.

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president