Human Rights commissioner Rosslyn Noonan says a new law giving non-police agencies greater powers to snoop is "chilling" and "disproportionately invasive".

The Search and Surveillance Bill, now before the justice and electoral select committee, sets out the powers police have to search and monitor people, but also extends powers to other agencies, such as the Commerce Commission and local authorities.

They will be able to secure warrants to use surveillance devices, such as cameras, search computers remotely and search vehicles without a warrant.

Ms Noonan said those agencies needed to justify having extra powers.

"It's quite chilling, really. In New Zealand we have the police force, which most New Zealanders have considerable trust and respect for ... with most of these other agencies the community as a whole wouldn't even know who they are and suddenly they have got all these powers."

She conceded the legislation needed to be updated but said many of the powers were disproportionately invasive given the agencies' responsibilities.

Other legal experts say the new powers, based on a 2007 Law Commission report, could be vulnerable to abuse.

Ralph Simpson, partner in commercial law firm Bell Gully, said police were trained and reasonably responsible in the use of surveillance powers, but other agencies were not qualified.

Agencies in Britain had received similar powers and had abused them, with some councils using surveillance devices "to detect dogs crapping on other people's lawns", he said.

Non-police agencies did not need surveillance powers and the police could do it for them if needed, he said.

"Why does the Overseas Investment Office need the ability to search my car?

"If you look at local government or the Commerce Commission, why do they need access to put video cameras or listening devices on private property? It's a pretty significant invasion of property."

Surveillance devices should be used on private property only to gather evidence on serious offending, he said.

Council for Civil Liberties spokesman Michael Bott said the extension of extra powers to these agencies raised serious concerns.

"Have these state agencies got Bill of Rights training and are they rights-sensitive? Have they got police training and institutional knowledge?"

A provision allowing police to require people to answer questions was "repugnant", he said.

Police Association vice-president Chris Cahill said it was important that agencies had powers to investigate in areas police could not, but they would need to be trained and use those powers appropriately.

The bill would also allow police to search without warrants if they thought there was evidence of a serious crime punishable by 14 years' jail or more, and that any delay could mean evidence was destroyed; and to detain a person at the scene of a search.

SNOOP AND SEIZE

Agencies such as the Commerce Commission and the Agriculture and Forestry Ministry will be able to:

Obtain warrants to use surveillance and tracking devices Ask a person to consent to a search of themselves, a place or vehicle.

Detain a person during a search of a place or vehicle Seize items in "plain view" without a warrant Stop and search vehicles without a warrant.

Source: The Law Society