Forty-nine businessmen and public housing officials have gone on trial, accused of taking bribes when President Jacques Chirac was mayor of Paris.
Ex-minister Drut was convicted in a case from Chirac's time as mayor
Prosecutors claim that during the 1980s and 1990s, housing department officials received bribes from contractors for licences to build council housing.
They say the money was used to fund Mr Chirac's Rally for the Republic (RPR).
Mr Chirac has denied any wrongdoing and is protected by presidential immunity from standing trial.
The latest trial follows last year's conviction of three ministers in another major corruption case.
They were found guilty of helping to rig public works contracts for the Paris region, from 1989 until 1997.
No politicians are involved in the current case, which is expected to last until April.
Mr Chirac was the mayor of Paris for 18 years, until he was elected president in 1995.
In 2000, he faced media allegations he knew of kickbacks paid to his party while mayor, based on a videotaped statement made by a former party official.
Mr Chirac refused to answer the claims, citing presidential immunity.