Prime Minister John Key says questions about former National Party MP Pansy Wong and her husband Sammy Wong are matters for the Audit Office.
Mrs Wong, the former MP for Botany, resigned from Parliament in December last year after misusing the international travel subsidy available to Members of Parliament.
The Auditor-General is investigating the couple's use of travel entitlements after intially deciding in December last year not to purse the matter.
The Labour Party is linking Mr Wong to Chinese companies involved in the KiwiRail tender process to build Auckland's new commuter trains.
But Mr Key says Mrs Wong is no longer an MP and he has no knowledge of that issue.
He is encouraging anyone with information to go to the Audit Office.