Italy’s parliament has expelled Silvio Berlusconi over his tax fraud conviction in a momentous move that raises the risk of his arrest but is unlikely to be the last act of his tumultuous career.

The three-time former prime minister told thousands of supporters outside his residence in Rome that he would “fight on” despite Wednesday’s vote, saying it was “a day of bitterness, a day of mourning for democracy”.

“We are not going to retire to some convent,” Berlusconi said in a defiant speech, as fellow senators began voting that ended up forcing him from parliament for the first time in his 20-year political career.

Motions put forward by Berlusconi’s allies in the Senate in an attempt to block the expulsion procedure were rejected one by one in a dramatic session in which dozens of lawmakers took the floor to support him.

One loyalist senator even compared the scandal-tainted Berlusconi to South African anti-apartheid icon Nelson Mandela and two rival senators almost came to blows.

Senate speaker Pietro Grasso said the failure of the motions meant that a proposal “abolishing the election of senator Silvio Berlusconi” was considered approved.

Berlusconi will now be banned from taking part in any general election for six years and will lose his parliamentary immunity, which offers safeguards against arrest.

Rumours are rife in Rome that an arrest could be imminent although Berlusconi’s lawyers have dismissed the prospect as “absurd” given that he has already had to give up his passport and is not a flight risk.

Experts said the expulsion marks another step in Berlusconi’s slow-motion demise, although he will continue to wield major clout even as an ex-lawmaker.

Opinions were mixed in the streets of Rome.

“We managed to put an end to 20 years of fascism, we can put an end to 20 years of Berlusconism too. I hope then we will become a more grown-up country,” said Giulio, a passerby in the trendy Trastevere district.

Several polls show that the 77-year-old Berlusconi’s popularity is undimmed among his core supporters and that a centre-right coalition led by him as figurehead could win a future election.

The political tensions come at an economically crucial time for Italy, which is struggling to end its longest post-war recession, and just as parliament debates a budget aimed at slashing high debt and deficit levels.

Prime Minister Enrico Letta has called for a “non-chaotic situation in Italy” and said a division within Berlusconi’s ranks “will help stability”.