The Italian Senate has expelled three-time ex-premier Silvio Berlusconi from Parliament over his tax fraud conviction.

The vote on Wednesday halts the 77-year-old Berlusconi's legislative run for at least six years, but does not mark the end of his political career.

Berlusconi had maintained his defiance ahead of the vote, declaring Wednesday a "day of mourning for democracy" before thousands of cheering, flag-waving supporters outside his Roman palazzo.

"We are not going to retire to some convent," Berlusconi said in a defiant speech, as fellow senators held rounds of voting that forced 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.

Many senators from his party wore black in mourning.

Even though Berlusconi will not hold a seat in Parliament, he is expected to remain influential in Italian politics. He has relaunched his Forza Italia party and analysts estimate he still has millions of supporters.

The Senate speaker declared he was ineligible for a seat in parliament after the house rejected a series of challenges by Berlusconi's supporters to a proposal for his expulsion. No formal vote was held.

The culmination of months of political wrangling, the vote on Wednesday opens an uncertain new phase for one of Italy's most divisive figures, who has dominated politics for two decades.

The former prime minister has asked fellow senators to delay the vote, claiming to have new evidence warranting a judicial review of his conviction, but it is expected to go ahead at 1800 GMT.

"Berlusconi is still extremely powerful, although that power is declining," said James Walston, a professor at the American University in Rome.

"He still has enormous resources, he still has his media, he still has lots of very diehard supporters inside and outside parliament."

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.

The vote comes at an economically crucial time for Italy, which is struggling to end its longest post-war recession, and just as parliament debates next year's budget.

Prime Minister Enrico Letta has called for a "non-chaotic situation in Italy," saying a division within Berlusconi's ranks "will help stability."

A group of dissidents led by Berlusconi's former protege, the deputy prime minister Angelino Alfano, broke away earlier this month to form their own group.

'Indelible stain'

But the coalition would have a much narrower Senate majority of around 10 seats, and could be vulnerable to sniping from Berlusconi even outside parliament.

Berlusconi has said a vote to expel him from parliament would be an "indelible stain" on Italian democracy.

"[It] would shame you in front of your children, your voters and all Italians," he said in an open letter to senators, maintaining the vote was "not about me, but about democracy."

Even some of Berlusconi's most hardline opponents have voiced doubts about the expulsion vote and the idea of beating the 77-year-old through the courts and parliament instead of at the ballot box.

Ejection from the Senate would also remove Berlusconi's parliamentary immunity, which offers a series of safeguards against the arrest of lawmakers, and observers say he is concerned about a possible arrest - although his lawyers dismiss the prospect as "completely unrealistic."

Berlusconi is currently appealing convictions for having sex with an underage prostitute, abusing the powers of the prime minister's office and leaking a confidential police wiretap to damage a political rival.

He also faces trial for bribing a leftist senator to join his party's ranks and could come under investigation for paying off young women who attended his raunchy parties to give favourable testimony.