Rome, September 9 - Premier Enrico Letta has said he is confident Silvio Berlusconi's People of Freedom (PdL) party will not sink the government before a meeting Monday of a Senate panel on whether to strip the centre-right leader of his parliamentary seat after a tax-fraud conviction. The PdL has threatened to withdraw its support for Letta's grand-coalition government if its main government alliance partner, the centre-left Democratic Party (PD), carries through with its stated intention to vote for Berlusconi to be stripped of his status as Senator on the panel. But the premier, whose executive was made possible by an unprecedented alliance between traditional foes in the PD and PdL in April after two months of deadlock followed February's inconclusive general election, said he was optimistic the government would not fall. "I'm sure that the PdL will decide for the best," Letta, a PD member, told the BBC. "I don't think it will leave the coalition. I don't know what will happen with the internal debate (within the PdL), but I'm working with the certainty that the government will continue to work and the parties will keep supporting the government". It may make more than a month for the Senate to reach a final decision on whether to strip Berlusconi of his seat after the supreme court upheld a four-year tax-fraud conviction against him last month - three years of which have been commuted because of an amnesty - making it definitive. A full Senate vote is required to make the ban effective but the PdL says it will not come to that if the PD votes against Berlusconi on the panel. The three-time premier risks losing his parliamentary seat under the terms of an anti-corruption law approved in 2012, which bans anyone with a conviction like the three-time premier's from holding office for six years. The PdL claims the law is being applied retroactively in Berlusconi's case, although it became effective before his definitive four-year conviction for fraud on film rights for his Mediaset empire on August 1. The PdL says the offences for which Berlusconi was convicted took place before the law was passed, and so it is being applied retroactively, which they say is against the Italian Constitution. The PD has dismissed arguments from jurists sympathetic to the PdL as "quibbling" and says the law must be applied to Berlusconi as it would be to anyone else. Berlusconi has appealed to Italy's Constitutional Court and the European Court of Human Rights against the ban from the tax-fraud conviction, which he blames, like his many other cases, on persecution by magistrates he says are left-wing.