NAPLES, Italy (Reuters) - Prosecutors on Thursday called for former Prime Minister Silvio Berlusconi to face another trial, on charges of bribing a senator, deepening the legal troubles of a key ally in Italy's coalition government.
A Naples judge must decide whether the evidence is sufficient to indict Berlusconi and order a trial.
The prosecutors accuse Berlusconi of having paid former Senator Sergio De Gregorio 3 million euros ($3.95 million) to defect from the small Italy of Values party shortly after the 2006 parliamentary election and join the center right.
His defection undermined then-Prime Minister Romano Prodi's government, which had a slim parliamentary majority, and contributed to its collapse in 2008.
De Gregorio has admitted taking money, and prosecutors asked that he stand trial alongside Berlusconi.
The request came a day after a Milan appeals court upheld a four-year prison sentence for tax fraud against Berlusconi, which will not take effect unless it is confirmed in a final appeal.
His People of Freedom party (PDL) is a key partner in Prime Minister Enrico Letta's right-left coalition government.
Berlusconi is already facing trial on charges of paying for sex with a minor in "bunga bunga" parties at his villa outside Milan.
He has denied any wrongdoing and says he is being persecuted by politically-motivated magistrates.
(Reporting by Amalia De Simone in Naples; writing by Steve Scherer; editing by Philip Pullella and Andrew Roche)