Italian Prime Minister Silvio Berlusconi dismissed calls to resign on Friday as pressure on his struggling centre-right government mounted and his latest verbal gaffe stirred outrage and exasperation.

Berlusconi, under pressure over corruption and sex scandals and facing criticism for his centre-right government's erratic handling of the economic crisis, accused the left-wing opposition of "obsessively" seeking to drive him from office.

"It is a demand I consider absurd, which would only create instability and which would open up new room for financial speculation," he said in a video message to party supporters.

"We have the numbers to reach the end of our term, as the constitution provides. And we will go ahead and complete our reform programme," he said, adding that he would remain in office even though it represented a 'personal sacrifice'.

Berlusconi left Rome on Friday for a private visit to Russia to celebrate Russian Prime Minister Vladimir Putin's birthday.

His comments came as students held marches across Italy to protest cuts to education spending and the financial crisis. In Milan, protesters threw paint at an office of ratings agency Moody's, which cut Italy's credit rating this week, and dumped rubbish in front of bank offices.

In Genoa, demonstrators gathered in front of a local branch office of the Bank of Italy.

Newspapers and opposition parties lambasted the premier over his latest verbal excess, a suggestion that his ruling PDL party rename itself with a vulgar slang term for female genitalia.

The term is also used to describe an attractive woman.

The remark, to party deputies in parliament on Thursday, drew criticism from the opposition which said it underlined Berlusconi's contempt for women.

"His misogynist jokes are offensive to women, who are considered less and less as people and ever more as 'goods' to be sold to the highest bidder," said Giuliano Carlino, a senator from the opposition Italy of Values party.

MOUNTING ATTACK

The 75-year-old prime minister has come under mounting attack as the financial crisis and growing divisions in his centre-right coalition fuel speculation that his government will collapse before the end of its term in 2013.

On Friday, ratings agency Fitch cut Italy's credit rating by one notch to A+ from AA- with a negative outlook, following a downgrade by Moody's on Tuesday, underlining market concern over the stability of its public finances and its chronically weak growth.

A 60-billion-euro austerity package to balance the budget by 2013 was passed last month only after weeks of hesitation and delay, while the timetable for a decree to pass economic reforms and approve the sale of state assets has slipped to Oct. 20.

So far, Berlusconi's majority in parliament has held up in repeated confidence votes but there has been mounting press speculation of a possible revolt within the PDL.

Groups as diverse as Italy's main business federation Confindustria, the head of the Catholic bishops' conference and the centre-left opposition have all attacked his government and made more or less open calls for him to resign.

Berlusconi, a self-made billionaire, is notorious for politically incorrect gaffes both on the diplomatic stage and at home, where his approval ratings have plunged.

He is facing three trials on corruption charges and one for allegedly paying for sex with an underage prostitute and he has also been drawn into a separate prostitution and extortion scandal which is being investigated by magistrates.