The leaders of Italy's two biggest parties are to meet Saturday to discuss a new electoral law, starting a process which could bring down the government of Prime Minister Enrico Letta and pave the way for snap elections, according to dpa. Changing the law is urgent, since the current system - dubbed "porcellum" or pigs' mess by the media - has been struck down by the Constitutional Court because it grants too many seats to election winners and limits voters' ability to choose their lawmakers. But the leader of the ruling centre-left Democratic Party (PD), Matteo Renzi, came under fire for choosing to discuss the reform with scandal-tainted former premier Silvio Berlusconi, whose conservative Forza Italia party is in the opposition. The meeting puts Berlusconi back in the political limelight, despite his legal troubles. He was ejected from parliament nearly two months ago due to a tax fraud conviction, which he is expected to serve in the coming months, doing community service. Smaller members of Letta's coalition government - such the New Centre Right Party of deputy premier Angelino Alfano - fear that Renzi and Berlusconi will cut a deal over their heads, and have threatened to quit the ruling alliance in protest. The left-leaning La Repubblica newspaper reported that Letta, in a tense meeting with Renzi late Thursday, had warned: "If you go ahead with Berlusconi, without (other) majority parties, I will resign on Sunday." The headline in Il Fatto Quotidiano, another daily that sympathizes with the protest Five Star Movement of comedian Beppe Grillo, read: "Today Renzi and Berlusconi can trip up the government." The two men were due to meet in the PD's headquarters in Rome at 4 pm (1500 GMT). Renzi said on television he would host his famously anti-Communist guest in a room complete with "a picture of Che Guevara and Fidel Castro playing golf." Renzi, who is also the mayor of Florence, is riding high in the polls. Since he was elected PD leader by a landslide in December, political commentators have speculated on his supposed ambition to oust Letta from the prime ministerial office. He denies any such scheming, and says a cross-party deal with Berlusconi is essential to give Italy more stable and solid institutions. He is pushing for wide-ranging reforms, including scrapping the upper chamber, the Senate, to streamline parliamentary procedures.