In Rome, violent clashes have left 50 police officers and at least 40 protesters injured.
The marchers set fire to cars, threw stones and overturned bins in Italy's worst street violence in recent years.
Mr Berlusconi's critics say he is too deeply mired in scandal and corruption allegations to remain in office.
The Italian prime minister, 74, is halfway through a five-year term but his position has been weakened by a series of scandals, largely involving his relationships with women.
He has also lost the support of his closest political ally, Gianfranco Fini, along with dozens of his supporters, depriving him of his automatic majority in the lower house.
Scuffles broke out in the lower house after opposition MP Katia Polidori voted in favour of Mr Berlusconi, and voting was briefly suspended.
Speaking in parliament, former anti-corruption judge Antonio Di Pietro - who now leads the opposition Italy of Values party - told Mr Berlusconi he was finished.
"Whatever the result of the vote you have bought, one thing is clear. You do not have a political majority that would allow you to govern," he said.
"Whether you like it or not, you have reached the end of the line for your political experience."
Last week, Mr Pietro made a formal complaint alleging that Mr Berlusconi was trying to buy votes. Rome magistrates have now begun an investigation.