Murray McCully is being threatened with legal action, over a new position being offered to Labour MP Shane Jones.
Mr Jones announced his retirement from Parliament last week, and is expected to take up a new Government position next month.
But, serial litigant Graham McCready claims both Mr Jones and Mr McCully could be breaking the law, if the job offer is accepted.
"Shane Jones has not accepted the bribe yet, but if he accepts the job he will then in my view have completed the offence."
Graham McCready is promising to launch a private prosecution, if the Serious Fraud Office fails to investigate the deal.