ROME — A court in Milan convicted former Prime Minister Silvio Berlusconi of tax fraud Friday and sentenced him to four years in prison. Berlusconi is also on trial over charges that he paid for sex with an underage prostitute. He has denied the accusation.

The ruling was Berlusconi’s fourth lower-court conviction, and the first since he stepped down as prime minister in November, after years in which his personal legal battles often eclipsed the work of his government. His four-year sentence was reduced to one year under a law aimed at reducing prison overcrowding.