Privacy Commissioner Marie Shroff has warned Parliament that a proposed law widening enforcement authorities' powers of search and surveillance needs more safeguards.

She says the Search and Surveillance Bill gives rise to "significant privacy issues".

"It does cover activities that are instrinsically invasive. One just can't get away from that."

Mrs Shroff said confidence that telecommunications were secure from intrusion "is an essential feature of private life and the ability to communicate freely".

The new law will bring together warrants for audio, visual and tracking surveillance devices.

Interception devices are now used in investigations of serious crime.

Rules for their use are spelled out in legislation such as the Crimes Act and the Misuse of Drugs Amendment Act, but there are few controls over visual surveillance.

The new bill gives wider scope for use of interceptions and tracking devices.

"Instead of being restricted to certain types of serious crime, enforcement officers will be able to apply for surveillance device warrants on the same basis as search warrants," Mrs Shroff told Parliament's justice and electoral committee, which is hearing submissions on the bill.

"You have got to balance that law enforcement need to make sure we can pursue the really nasty people with a public interest in privacy and making sure we strike that right balance."

Mrs Shroff said she generally supported the bill, which is the result of an extensive review and report by the Law Commission.

National and Labour support it as a way of countering the growing sophistication of criminals and technology.

Mrs Shroff said the bill needed major changes to address privacy concerns.

She wants the section on computers tightened to stop enforcement agencies going on "trawling exercises", saying the authorities should be required to say what they are looking for.

She said "production orders" - requiring people to produce information - were now limited to specified serious offences.

Under the bill, they could be used for any offence for which a search warrant could be obtained.

"This is a significant change in the law, and will dramatically increase the availability of production and monitoring orders.

"These orders potentially make a vast amount of information available to enforcement officers."

Mrs Shroff was also concerned that production orders could be issued without being examined by a judge.

"Traditional expectations are that intrusions will not be made in private communications without rigorous oversight by a judge.

"We believe the orders should be issued by judges only."

This was because of the wide-ranging nature of production orders, and because they were "turbo-charged by technology".

* Removes right to silence for person suspected of having evidence in crime with three or more suspects.
* Widens provision for searches without warrant.
* Allows copying of material stored on computers and remote searches of computers.
* Increases covert investigative powers of the Commerce Commission, the Reserve Bank, Customs and Ministries of Agriculture and of Fisheries.
* Gives power to detain anyone at scene of search.

* Require enforcement officers to notify the subjects after the surveillance has finished.
* Stop computer searches becoming trawling exercises.
* Limit to judges only the right to issue production orders.