The plainclothes officers arrived a few hours before Berlusconi was set to confront his main rival Achille Occhetto, leader of the ex-Communist Democratic Party of the Left, in the key television debate of a long and bitter campaign.
Police said two officers of the elite DIGOS political branch entered Forza Italia's Rome headquarters to obtain a list of the conservative movement's candidates in the March 27-28 election.
They acted at the request of deputy public prosecutor Maria Grazia Omboni, from the southern Calabrian town of Palmi, who is investigating links between freemasons, politics and crime. Her reasons were not immediately clear.
Berlusconi said in a statement: "Such things have never happened before in our democracy. These things happen only in totalitarian countries. In a free country the voters are the judges of the parties which seek their support."
He said he had requested a meeting with President Oscar Luigi Scalfaro "to end this provocation against the freedom of Italians."
The raid took place as a mud-slinging match raged between Berlusconi and his political opponents over allegations that Forza Italia was the Mafia's choice in the elections
The row reached fever pitch on Tuesday night when Berlusconi demanded the resignation of the chairman of parliament's anti-Mafia commission, leftist politician Luciano Violante.
Violante was quoted by La Stampa newspaper on Tuesday as saying that Marcello Dell'Utri, head of Berlusconi's Publitalia advertising agency and the driving force behind Forza Italia, was on a list of suspects in an investigation into drugs and arms trafficking by the Sicilian Mafia.
Violante has denied making the remarks, which magistrates say are untrue.
A Message from The Moscow Times:
Dear readers,
We are facing unprecedented challenges. Russia's Prosecutor General's Office has designated The Moscow Times as an "undesirable" organization, criminalizing our work and putting our staff at risk of prosecution. This follows our earlier unjust labeling as a "foreign agent."
These actions are direct attempts to silence independent journalism in Russia. The authorities claim our work "discredits the decisions of the Russian leadership." We see things differently: we strive to provide accurate, unbiased reporting on Russia.
We, the journalists of The Moscow Times, refuse to be silenced. But to continue our work, we need your help.
Your support, no matter how small, makes a world of difference. If you can, please support us monthly starting from just $2. It's quick to set up, and every contribution makes a significant impact.
By supporting The Moscow Times, you're defending open, independent journalism in the face of repression. Thank you for standing with us.
Remind me later.