Berlusconi Senator-buying trial gets underway
Prodi's 2006-2008 govt fell after losing support in Upper House11 February, 11:09
Valter Lavitola, an associate of the ex-premier's, is also on trial for allegedly acting as a go-between.
Prosecutors have claimed Lavitola also tried to bribe other Senators who have not been identified.
Berlusconi is accused of paying De Gregorio a bribe of three million euros to leave the centre left and join the centre right, helping to undermine the 2006-2008 government of Romano Prodi.
De Gregorio has admitted not declaring to the tax authorities two millions euros he received and plea-bargained a 20-month sentence.
De Gregorio has not gone to jail because sentences under two years are automatically suspended.
Prodi's 2006-2008 government fell after losing the support of the Senate, leading to new elections that Berlusconi won.
Senate Speaker Piero Grasso announced last week that the Upper House would request to be made a civil plaintiff in a trial, prompting howls of protest from Berlusconi's Forza Italia party.
The case is only one of a series of legal woes for billionaire tycoon Berlusconi, the charismatic centre-right leader who was ejected from the Senate and last year after a definitive conviciton for tax fraud at his media group, his first binding conviction in 20 years of judicial battles.
The three-time premier is appealing two convictions by courts of first instance: one for paying for sex with an underage prostitute and abusing his office as premier to try to cover it up; and another for involvement in the publication of an illegal wiretap.
The Forza Italia leader says he has been targeted by politically motivated magistrates since he entered politics in 1994.