"Be aware that your prime minister no longer has any kind of cell phone because he is subjected to every kind of wiretapping," Berlusconi told a meeting of his ruling conservative People of Freedom party in the northern city of Milan.
"Everyone considers it an infringement of liberty not to be able to speak freely on the phone. This is why I have stepped backwards in time and no longer use a mobile phone," Berlusconi said.
Berlusconi currently faces four criminal trials. Following a ruling by Italy's constitutional court last month that removed his automatic immunity from prosecution, a tax fraud trial re-started against him in the northern city of Milan on Monday.
Two related trials against Berlusconi involving tax fraud, embezzlement and bribery are due to resume in early March.
But in a fourth and possibly more damaging case relating to Berlusconi's private life, a judge has ordered him to stand trial in April for allegedly paying an underage nightclub dancer for sex and abusing his powers of office to get police to release the girl from custody on unrelated theft charges.
If convicted of both offences, 74-year-old Berlusconi could be sentenced to up to 15 years in prison.
The judge who sent Berlusconi to trial over the prostitution case ordered a fast-track trial with no pre-trial hearing due to the "obviousness" of the evidence, which is contained in over 700 pages of wiretaps transcripts and documents.
Berluconi denies wrongdoing in all the cases, saying he is the victim of an alleged conspiracy of leftist judges.
He has claimed he is the most persecuted politician in the history of the world.