Italian Prime Minister Silvio Berlusconi faces a crucial confidence vote amid infighting in his ruling coalition as well as growing criticism over his handling of the economy and mounting legal scandals.

Barring any major upsets, Berlusconi's majority is expected to pass the vote but the margin is likely to be narrow and unlikely to strengthen the coalition, reassure the markets or put an end to growing calls for the premier to resign.

"There is no alternative to this government," the scandal-tainted 75-year-old prime minister told parliament on Thursday, saying that the centre-left opposition was "united only by its anti-Berlusconism."

"Early elections would not solve the problems we have... A political crisis now would mean victory for the party of decline, catastrophe and speculation."

Berlusconi has been forced to turn to parliament to confirm its support after the ruling coalition suffered an embarrassing setback on Tuesday when it was unexpectedly defeated in a low-profile but important technical vote.

Opposition parties boycotted both the premier's speech on Thursday and the debate ahead of the confidence vote on Friday.

The vote is expected at around 1030 GMT.

Berlusconi's allies are confident it will pass. Denis Verdini of the ruling People of Freedom (PDL) party said he expected 318 or 319 members votes in favour -- beating the opposition by some 10 votes, according to press reports.

But Daniela Santanche, a close ally and deputy from the PDL, said the vote would only allow a shaken government to "patch things up" for now.

The embattled premier's speech on Thursday was slammed as lacking in concrete proposals to tackle Italy's most pressing problems -- from high youth unemployment to weak growth -- and failed to reassure political commentators.

The Corriere della Sera daily spoke of an "atmosphere of interminable agony which weighs on the government." The coalition is likely to survive the vote of confidence, it said, but is "struggling towards the end of the line."

"We are living through the long decline of a government," said Stefano Folli from Il Sole 24 Ore newspaper.

The defeat in parliament has revived talk about possible plots against Berlusconi from within the government's own ranks. His popularity is at an all-time low, with a poll last month giving him a 24-percent approval rating.

He is also a defendant in three trials for bribery, tax fraud, abuse of power and paying for sex with a 17-year-old girl -- and at the centre of an array of other sex scandals.

His joke last week that his party should change its name to "Go Pussy!" fell flat and incensed many who are concerned he is damaging Italy's image abroad.

Former Berlusconi allies such as ex-economic development minister Claudio Scajola have begun voicing their discontent -- and there have been rumours for months as to where Finance Minister Giulio Tremonti's allegiances lie.

Political uncertainty in Italy and its effect on long-term economic policymaking was cited as a key factor for the recent downgrades of its sovereign debt by ratings agencies Standard & Poor's, Fitch and Moody's.

Some commentators say Tuesday's vote defeat was one more step in the decline of Berlusconi's political career, which began in the early 1990s, and say the government is unlikely to see out its mandate which ends in 2013.

Others however argue that it is too early to dismiss the canny Berlusconi.

On the streets meanwhile, a protest movement similar to the "Indignants" in Spain and "Occupy Wall Street" in the United States has been taking shape.

Tens of thousands are expected to turn out for a rally on Saturday.