The Green Party wants the Security Intelligence Service (SIS) reviewed to assess whether the country needs it.
MP Keith Locke put this to Parliament's security and intelligence committee today in a submission on a bill that strengthens the laws around the agency.
Public submissions on the Security Intelligence Service Amendment Bill are being held in secret, against the wishes of the Greens and the Labour Party.
Mr Locke released his written submission to the media, which he is allowed to do, and said there was no need to hold secret hearings.
The bill puts into law specific provisions for the SIS to carry out its surveillance activities and updates the legislation to cover high-tech communications.
Mr Locke said in his submission the SIS had too many powers to invade people's privacy, without providing sufficient justification, and the committee met only for a few hours a year.
The committee is chaired by Prime Minister John Key and its members are MPs from Labour, the Maori Party, ACT and the Greens.
"It is not a true select committee and there is no sign that its oversight of the SIS has much rigour," Mr Locke said in his submission.
"The Inspector General of Intelligence and Security has limited ability to correct mistakes, and receives relatively few complaints largely because most people whose lives are negatively affected by SIS assessments would not even know if they were under surveillance."
Mr Locke said the agency's legal mandate meant it acted as a restraint on the freedom of speech and political activity.
"Instead of proceeding with this legislation, it would be better for the Government to initiate a review of the SIS, with public input, to assess whether we really need this secret agency," he said.
Earlier today the Council of Trade Unions (CTU) also released its submission on the bill, saying the SIS could be able to create an army of informants immune from prosecution.
"We are concerned that this bill sets up structures that will enable random surveillance without sufficient authorisation, at an extreme leading to a situation where there could be a wide network of informants throughout society," CTU president Helen Kelly said.
"While this may not be the intent, we should not set up structures that would allow such outcomes."
Ms Kelly said the CTU was also concerned the bill would have an impact on trade unionists and negatively affect free speech, political activity and privacy.
NZPA