Independent MP Peter Dunne has started negotiations with the Government about potential support for new spying laws.
The legislation will allow the Government Communications Security Bureau to spy on New Zealanders, when assisting other law enforcement agencies.
It also has the power to carry out surveillance to protect national security and to help combat cyber crimes.
Mr Dunne has confirmed he is in discussions with the Government, which needs at least one more vote to progress the bill.
However, he said in the past that he does not believe the GCSB should have any role in domestic surveillance under any circumstances.
Opposition parties say that is the whole point of the new bill, so it is hard to see how Mr Dunne could support it - even with major amendments.