Tanzi has already been sentenced to a 10-year prison sentence on market-rigging charges and filing false reports with regulators in the wake of the collapse of Parmalat, the ANSA news agency reported
Prosecutors, however, are now asking for an additional 20-year sentence for a separate set of fraud and criminal conspiracy charges.
The case involves 25 defendants, including Tanzi. In addition, Tanzi and more than 50 former Parmalat employees are involved in two other trials having to do with the firm's collapse.
The investigations began with Parmalat's bankruptcy in 2003, after which it was discovered that $5.3 billion reportedly held in a Bank of America account did not exist.
The executives of the firm have been accused of share price manipulation and using bond issues to cover their mistakes. In the aftermath of the bankruptcy, about 150,000 investors found the bonds they had purchased were worthless.
Although sentenced to 10 years in prison, media reports say it is rare for someone in Italy to serve time at an advanced age. Tanzi, who is 72, was held for several months in jail in 2004, CorpWatch reported.