Labour is calling on the Government to release the text of an agreement that it says affects thousands of Americans living in New Zealand.
The Government has signed an inter-governmental agreement with the United States to supply the contact details, bank account numbers and transaction records of American citizens who live here.
Legislation allowing Inland Revenue to collect such information for the IRS has passed its second reading in Parliament.
Labour revenue spokesperson David Clark said MPs are being asked to pass legislation empowering an agreement that they have not seen.
He said it is not clear why the Government is withholding it.