Monaco-based businessman, Owen Glenn, has made written statements to the Serious Fraud Office and Parliament's Privileges Committee about donations to New Zealand First leader, Winston Peters.
The Privileges Committee is considering whether Mr Peters should have declared a $100,000 donation by Mr Glenn towards his legal expenses for an electoral petition in 2006, on the register of pecuniary interests.
The Serious Fraud Office is considering a formal investigation after the ACT Party complained that Mr Peters was refusing to answer questions about party donations.
Mr Glenn says he will co-operate with both the Serious Fraud Office and the Privileges Committee as may be necessary, but has not released the detail of statements to either body.
He says he won't make any further public comment.