UPDATE 1-Opponents tell Berlusconi to quit over sex scandal
* Opposition demands Berlusconi resign
* New transcripts show Berlusconi's sexual boasts
* Wiretaps prompted two Finmeccanica execs to step down (Adds Northern League comments, Finmeccanica details)
ROME, Sept 18 (Reuters) - Italian Prime Minister Silvio Berlusconi faced growing pressure on Sunday to resign after embarrassing new revelations of parties and young women prompted questions about his ability to govern a country rocked by financial crisis.
Italian newspapers in recent days have replaced front page headlines on soaring bond yields and sliding shares with wiretapped chats between Berlusconi and Giampaolo Tarantini, a businessman suspected of providing prostitutes for the premier.
In one excerpt published by the Corriere della Sera daily, Berlusconi boasts of champagne-filled partying till 6:30 am at a Milan nightclub and pocketing eight phone numbers of women. He also brags of fending off a line of 11 girls outside his door and "doing only eight girls, because I couldn't do more".
"If you have a girl -- two girls, three girls -- to bring," Berlusconi is quoted as asking the southern businessman ahead of their next encounter, "please don't get tall ones ... because we are not tall."
In another excerpt reported by major dailies, Berlusconi says "Gianpi" and his female friends could come along on the premier's flight to Milan. Yet another has him joking to a young woman that he is premier in his "spare time".
Opposition parties stepped up calls for Berlusconi to resign after the latest disclosures, saying a country immersed in a debt crisis that threatens the entire euro zone could not afford a premier who governs in his spare time.
"Is there a single reason comprehensible to the world on why Berlusconi should not resign?" Pier Luigi Bersani, leader of the centre-left Democratic Party said.
Berlusconi loyalists, however, rallied to defend the premier and said he would not bow to demands to step aside.
"Berlusconi does not have any desire to resign," said Angelino Alfano, secretary of Berlusconi's People of Freedom party.
Berlusconi has kept up a defiant attitude through various scandals, blaming his old foes -- "Communist" magistrates and a "leftist" press -- for hounding him mercilessly.
The media mogul maintains his private parties were elegant, convivial affairs and his lawyer says the premier was unaware of any links between Tarantini and prostitution.
Tarantini was arrested with his wife earlier this month on suspicion of extorting money from Berlusconi in return for his silence over the prostitution allegations.
He is also suspected of procuring women for Berlusconi in a bid to curry political favours and win contracts, including some with Italian defence and aerospace giant Finmeccanica.
Finmeccanica has not been charged with wrongdoing and says it has never given contracts to Tarantini or to another businessman who was also named in the wiretaps. Two executives at the firm resigned last week after their names cropped up in published excerpts of wiretaps from judicial probes.
The latest disclosures form an ever-more complicated web of scandal and legal headaches around the beleaguered premier, who has hung on despite a barrage of lurid scandals over the years.
His wife has sought divorce after accusing him of cavorting with minors, while the infamous "Rubygate" affair has seen him accused of paying for sex with a teenage prostitute.
Revelations of "bunga bunga" parties with escorts and showgirls angling for jobs in his media empire have prompted incredulity and sniggers, but failed to push him out of power.
Still, the latest disclosures come at a sensitive time for the premier, who is grappling with slumping ratings, frustrated allies, a financial storm that has driven up Italy's borrowing costs and an unpopular austerity package.
Adding to the confusion, Berlusconi's volatile ally Umberto Bossi on Sunday reiterated a call for the secession of Italy's rich north at a speech to his Northern League party faithful.
Faced with the League's sliding popularity among voters in its northern home base, Bossi has stepped up his familiar rhetoric of a hard-working north paying for a profligate south and expressed doubts about the government seeing out its term.
Still, he has so far remained loyal to Berlusconi in parliament, ensuring the media mogul stays in power. (Editing by Peter Graff)