Key Points:

The Police Minister will meet the Police Commissioner today before deciding if an investigation is needed into police spying on protest groups.

The Special Investigation Group, set up in 2004 to focus on terrorism threats to national security, has been reportedly paying informants to spy on groups such as Greenpeace, animal rights and climate change campaigners and Iraq war protesters.

Police Minister Judith Collins said she would decide whether to launch an inquiry after her meeting with the Police Commissioner, Howard Broad, today.

"I want to find out more information before I say anything more," Ms Collins said.

"I have not been briefed on this issue at all yet and I am also keen to find out what, or how much, former Police Minister Annette King knew about this."

Rob Gilchrist, from Christchurch, a key member of various protest and community groups such as Greenpeace in the past decade, was paid to pass on information to the SIG on planned protests, and group members' personal information and sexual relationships, the Sunday Star-Times reported.

He had sent information to an anonymous email address traced to two Christchurch SIG officers, Detective Peter Gilroy and Detective Senior Sergeant John Sjoberg.

A police spokesman would neither confirm nor deny the existence of any informant within any group.

Mr Gilchrist's work with the police was discovered by his girlfriend, animal rights and Labour Party activist Rochelle Rees, who was helping him fix his computer.

Miss Rees said they met at an animal rights meeting. She thought their relationship had been based on common values and goals, and was devastated to learn that he had been spying on her.

"I am disgusted at the police, both for their extreme level of intrusion into my life, and for the way they have used Rob and had him live a lie for 10 years."

This year, Mr Gilchrist said Thompson Clark Investigations, an investigations company employed by Solid Energy, offered him money for information about the anti-mining group Save Happy Valley Coalition.

Coalition spokesman Alan Liefting said although it was frustrating that private investigation firms paid members to infiltrate protest groups, it was "totally disgusting" for the police to be doing the same.

"This is not Russia, and New Zealand shouldn't be turned into a Big Brother police state," Mr Liefting said.

He believed Mr Gilchrist, who has been involved with the coalition, was paid about $600 a week by the police.

"My beef is really with the police for dangling money, public money, in front of protest group members, such as Gilchrist, in an attempt to [turn] them into spies," Mr Liefting said.

"Is this not a waste of police resources?"

Green Party police spokesman Keith Locke attacked the police surveillance as Stasi tactics and covert political operations that undermined democracy.