''In his head Berlusconi makes no distinction between truth and lies,'' Bersani told state broadcaster Rai 1.
Bersani, of the center-left Democratic Party, criticized Berlusconi's campaign for sending out a letter, promising citizens a refund for a contentious new property tax paid on primary residences in 2012, Italy's ANSA news agency reported.
"I have also seen people, the elderly, misunderstand ... . It was a major impropriety," Bersani said.
Bersani told ANSA he believes the Italian budget deficit is doing better but since Prime Minister Mario Monti took over from Berlusconi, who is running for the job again on the center-right People of Freedom party ticket, 14 months ago, the country's economy has been worse.
"The deficit is beginning to come under control but it is the real economy that isn't moving," said Bersani, who claimed responsibility for whatever liberal reforms that have been made.
"The only liberal things in this country were done by me," he told Rai 1. "I won't take lessons from a right that is populist and supports a strong state, or from Monti."
Italy will vote for its next prime minister in parliamentary elections scheduled Sunday.