The Commonwealth prosecutor's office has revealed disgraced Tasmanian businessman John Gay made more than $3m through insider trading, and has vowed to pursue the funds.

The Commonwealth Director of Public Prosecutions (CDPP) is pursuing the money Gay made in a series of illegal trades between December 2 and 10, 2009.

Gay chaired the timber giant Gunns for eight years until 2010.

Gunns went into voluntary administration in 2012, just weeks after announcing a $904 million loss.

Investors lost more than a billion dollars.

Gay was convicted last year of selling 3.4 million Gunns' shares while he had price sensitive information.

The courts fined him $50,000 and disqualified him from acting as a director of any company for five years, a ban overturned by the Supreme Court this year.

Earlier estimates suggested Gay had made almost $1 million from illegal trading.

But now the CDPP calculates his windfall to be almost $3.1 million and will pursue the money under the Proceeds of Crime Act.

The application still has to go before the Supreme Court and a date is yet to be set for that hearing.