By James Mackenzie

ROME (Reuters) - Italian Prime Minister Silvio Berlusconi dismissed opposition calls to resign on Friday after yet another vulgar gaffe stirred up a mix of outrage and weary exasperation.

Berlusconi, under pressure over a variety of corruption and sex scandals and facing criticism over his center-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 program," he said, adding that he would remain in office even though it represented a "personal sacrifice."

Berlusconi's comments came as 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 joking remark, to a group of party deputies in parliament on Thursday, drew severe 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," Giuliano Carlino, a senator from the opposition Italy of Values party said.

MOUNTING ATTACK

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

This week's downgrade of Italy's sovereign debt rating by Moody's underlined 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 after weeks of hesitation and delay while the timetable for a decree to approve the sale of state assets has also slipped to Oct 20.

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

Groups as diverse as Italy's main business federation Confindustria, the head of the Catholic bishops' conference and the center-left opposition have all attacked his government.

Berlusconi, a self-made billionaire, is notorious for politically incorrect gaffes both on the diplomatic stage and at home, where he appears to believe they still endear him to macho Italians despite his plunging approval ratings.

He is facing three trials on corruption charges and one for having sex with an under-age nightclub dancer.

(Reporting By James Mackenzie, editing by Barry Moody)