The Labour Party is accusing the Government of blindly passing legislation, which allows private data of New Zealand taxpayers to be given to United States authorities.
Revenue Minister Todd McClay told the Revenue select committee at Parliament on Wednesday that he hasn't seen the detail of the agreement.
The new law means financial institutions will have to give details of its taxpayers that are US citizens or US permanent residents in New Zealand to America's tax department. These include contact details, bank account numbers and transaction records.
Legislation allowing Inland Revenue to collect such information for the IRS is going through Parliament.
Mr McClay told the committee he hasn't seen a final copy of the agreement, and that it is an operational matter.
But Labour's revenue spokesperson David Clark says that's outrageous.
"I was horrified that the minister hadn't even asked to see the agreement. On the one hand, he said that he was confident that it was going to be fine; and on the other hand, he hadn't really been across the detail at all. So those two things can't be true - unless he's not doing his job properly."
The law is set to take effect from July this year.