Berlusconi has already asked the European Court of Human Rights in Strasbourg, France, to weigh in on his quest to keep his Senate post.
Berlusconi's bid "is surely an element we will reflect on, but it's an event external to the panel's work," said Stefania Pezzopane, a center-right leader who is a vice president of the panel. Her comment seemed to indicate that the panel wouldn't wait for any decision by the court, which, even if it agrees to rule on the ex-premier's petition, could take months.
She expressed the sentiment of several other panel members when she called the intent of the 2012 law "very clear" anyone with a prison term exceeding two years is ineligible to serve, whether the crime was committed before or after the law's passage.
The People of Freedom party panel member who pitched for Berlusconi to hold on to his seat told reporters that the Strasbourg court bid was only a "fragment" of the former premier's strategy.
A Milan appeals court and a lower court had found Berlusconi guilty of artificially inflating the amounts paid for film rights by his Mediaset empire to reduce the company's tax liabilities. The Milan court also issued a ban against holding office, and a separate court must still determine the length of that ban from one to three years. That ban isn't related to the one the Senate is debating.
Letta's center-left Democratic Party says the 2012 law must be applied, and that Berlusconi's challenge is simply another last-ditch effort to save himself from his own legal woes.
Still, a top Democratic Party member and even Italy's justice minister have said the constitutionality of the law could be reviewed by Italy's Constitutional Court, given that several legal scholars have questioned whether the ban is retroactive.
Letta, for his part, has tried to sound confident that Berlusconi's allies won't pull the party's support for his government.
"I think they won't leave the coalition," Letta told the British Broadcasting Corp in an interview.
Because of a law to reduce prison overcrowding, Berlusconi's four-year sentence was automatically reduced to one year. And because of his age he turns 77 later this month he is eligible to serve the punishment under house confinement. He can also opt to do a year of community service, but hasn't said publicly what he will choose.