Italy faces a government crisis and possible early elections with the eruption of open warfare between Prime Minister Silvio Berlusconi and the former ally who is now his fiercest rival.
Lower house speaker Gianfranco Fini demanded on Sunday that the prime minister step down to allow the formation of a new centre-right coalition, possibly without Berlusconi at the helm.
Weakened by a series of sex scandals, Berlusconi made it known through aides that he had no intention of giving in to Fini's demands, meaning a showdown will most likely take place in parliament in the next few days.
"The government is on the brink of collapse," headlined the leading Corriere della Sera newspaper.
Berlusconi and Fini jointly created the People of Freedom Party (PDL) in 2008 to unite the centre-right, but Fini set up his own movement, the Future and Freedom for Italy (FLI), after the prime minister expelled him last July.
At a dramatic conference of his new party, Fini said Berlusconi should resign immediately for the good of Italy because the centre-right that made up the PDL when it was founded no longer existed, and a new programme was needed.
He said if Berlusconi agreed to resign, the FLI, which controls around 40 seats in parliament, would consider supporting a new Berlusconi-led government, but only if he signed up to a set of conditions and a new centre-right agenda.
"The gauntlet has been thrown down, and with a vengeance. Fini has finally come out into the open from his guerrilla warfare and has declared open war," said James Walston, political science professor at the American University of Rome.
Fini said that if Berlusconi did not resign, one minister, one deputy minister and two undersecretaries loyal to Fini would resign, forcing Berlusconi to either reshuffle his cabinet or risk a confidence vote in parliament.
Berlusconi does not have a majority in the lower house without deputies loyal to Fini, so the FLI could bring down the prime minister if it voted with the opposition.
BOLD ULTIMATUM, RISKY GAMBLE
Fini's ultimatum is seen by most commentators as a bold attempt — and a risky gamble — to shove Berlusconi aside as centre-right head.
"Fini succeeded once again in passing on the responsibility for early elections and potential chaos to Berlusconi," Walston said.
The Northern League, a key coalition component, was meeting on Monday afternoon in Milan to decide its position.
Political commentators said Berlusconi would be loath to step aside willingly because if he were unable to form a new government, he would have to move aside and let someone else from the centre-right try.
If a new government cannot be formed with the aim of lasting until the end of the current legislature in 2013, Italy would be forced to hold early elections, probably next spring.
Significantly for Berlusconi, his judicial woes would immediately return to haunt him if he left office.
He is exempted from attending a trial where he is accused of corruption. A law which allows him to skip court appearances while he is prime minister would no longer protect him.
On Sunday Fini made several allusions to Berlusconi's recent private problems, saying Italy's image in the world right now was less than stellar, and speaking of "moral decay".
Italy has been transfixed for days by the story of a teenaged nightclub dancer known as Ruby who received 7,000 euros ($9,830) from Berlusconi after attending a party at his sumptuous private villa outside Milan earlier this year.
He has shrugged off a storm of criticism over the incident, even stoking the outrage in his trademark provocative style by remarking "it's better to like beautiful girls than to be gay".
Berlusconi has survived previous scandals over parties and prostitutes but Fini appears to have gambled that this time the national mood is different.
