Rome, February 20 - Ex-premier Silvio Berlusconi is trying to buy votes with taxpayers' dollars, a political opponent from the left-wing Civic Revolution party said in a formal complaint filed to prosecutors Wednesday. In a statement to prosecutors, Gianfranco Mascia - a candidate for the regional council in Lazio province - charges that Berlusconi's campaign promise to refund a hated housing tax if elected next week amounts to money for votes. Berlusconi, who founded the People of Freedom (PdL) party, has promised that if elected on Sunday and Monday, he would rollback an IMU housing tax introduced in 2012 by caretaker premier Mario Monti. He also promised to refund four billion of euros collected in the tax. That's bribery, says Mascia, a member of the Civic Revolution party headed by prosecutor Antonio Ingroia. "To obtain a refund for (the housing tax) IMU 2012, you have to vote for the PdL". He also complained that Berlusconi's campaign mail-outs to Italian homes amount to a "scam" because the envelopes, bearing a signed letter from Berlusconi, claim to contain an IMU refund.