Independent MP Peter Dunne says he won't support the new spy agency legislation unless changes are made to satisfy his concerns about the protection of citizens' private information.
The Government needs Mr Dunne's vote to pass the bill, which would allow the Government Communications Security Bureau to legally spy on New Zealanders.
Prime Minister John Key has agreed to Mr Dunne's proposal for a three-person oversight panel, with two people sitting alongside the Inspector-General of Security and Intelligence in an advisory role.
Mr Dunne says the review panel is a good start, but remains unconvinced that the bill in its current form provides enough protections to individuals and their private information. He says he doesn't want to go into too much detail about other changes under negotiation.
John Key says he wants to secure Peter Dunne's vote, which would be enough to pass the bill, but is willing to talk to other parties to build a larger majority. He says he would be open to a review of the GCSB, along with the SIS, as early as 2015 if that would get the Labour Party's support for the legislation.
But Labour leader David Shearer says that is unacceptable. "What we want is the review before the law, rather than afterwards. It's not good enough to simply say, 'We'll rush through this law and if it's broken we'll fix it up in three or four years' time' - that doesn't make any sense."
Mr Key says he will talk to Mr Shearer at a meeting of Parliament's Intelligence and Security Committee this week.
New Zealand First leader Winston Peters says there has still been no formal approach from the Government about potential support from his party. He says the oversight panel was his party's idea, but it would not have enough power and it's not a strong enough compromise to win his support.
Internet NZ supports significant changes
Internet New Zealand is encouraging politicians negotiating changes to the bill to stick up for the concerns raised at the select committee and make sure the bill is significantly changed.
The group's chief executive, Jordan Carter, says that is a positive step, but it is not enough to tackle the concerns people have voiced. He says Mr Dunne and Mr Peters are in a strong position in regard to this legislation and hopes they use their negotiating power to make it workable.
Mr Carter says so far any proposed changes are just about oversight, not about the powers of the agency itself.
Lawyer doubts review panel's effectiveness
A human rights lawyer doubts how effective a review panel for the Government Communication Security Bureau would be.
Human Rights Foundation spokesperson Tim McBride says anything that increases the level of oversight and protects people's rights is a good thing, but questions how effective in practice these safeguards are likely to be.
Mr McBride says the other concession being floated - of a review of all the Government's spy agencies - would be better and should happen sooner rather than later.