By Naomi O'Leary
ROME (Reuters) - Politicians in Italy's fragile coalition government traded increasingly heated barbs on Saturday over a tax conviction that threatens the political future of center-right leader Silvio Berlusconi.
The former prime minister has told his party to demand reform of the justice system - which he maintains found him guilty of tax fraud because of political bias - or withdraw from a delicate coalition with the center-left Democratic Party (PD) that has so far lasted three months.
Financial markets have shrugged off the upheaval until now, but strife in the coalition threatens efforts to revive an economy mired in its longest post-war recession.
On Friday, five ministers from Berlusconi's People of Freedom (PDL) party said they were ready to resign if needed, and senior party officials agreed to lobby President Giorgio Napolitano to issue a pardon. The party has called a Sunday demonstration in central Rome in support of Berlusconi.
Deputy Economy Minister Stefano Fassina, a senior member of the Democratic Party, called the request for a pardon "an unacceptable provocation, as is the request to put the judiciary under political control."
Fassina told television SkyTG24 on Saturday: "Either the PDL returns to normal democratic channels, or the PDL ministers who threatened to resign should do it."
The tax conviction could put Berlusconi under house arrest or in community service for a year and cost him his seat in parliament after two decades as the dominant force in Italian politics.
He has vowed to continue his political activities, and on Saturday a newspaper controlled by his family printed a picture of his daughter Marina on its front page with the caption: "The future of the center right."
A senior official in Berlusconi's party, Sandro Bondi, said the billionaire media mogul must be allowed to stay in politics "or Italy truly risks a sort of civil war with unpredictable outcomes for all".
"We advise Bondi to wear a hat, drink lots of water and avoid alcoholic drinks in the heat. Certain statements can only be explained by this," said PD deputy Ernesto Carbone as the temperature in Rome approached 40 degrees Celsius (104 degrees Fahrenheit).
(Reporting by Naomi O'Leary; Editing by Ruth Pitchford)