An activist who found out her ex-partner was spying on a number of protest groups is shocked police felt a need to spy on them.

Rochelle Rees, an animal rights and Labour Party activist, discovered her then-partner Rob Gilchrist had been paid by police to spy on protest groups when she helped him fix his computer about seven weeks ago.

Mr Gilchrist, heavily involved in various campaigns and protests over the past decade, was paid to pass information on the groups' plans and members to the police Special Investigation Group (SIG), set up in 2004 to focus on terrorism and threats to national security.

Ms Rees said she felt betrayed by Mr Gilchrist but equally appalled the SIG was spying on them.

The SIG had monitored Greenpeace, animal rights and climate change campaigners, and Iraq war protesters, the Sunday Star-Times reported.

"There is no reason why police needed to be spending money spying on us," she told NZPA.

"I've never heard of violent protest in New Zealand other perhaps than the National Front and their like."

Ms Rees said she thought the SIG was targeting groups like the ones she was connected with almost out of boredom.

"They were set up as a counter-terrorism group but there aren't any national security issues in New Zealand," she said.

"They have been given all these resources and they have to justify their existence so they are targeting us instead."

She was equally appalled to see incoming Police Minister Judith Collins saying paid informants might sometimes be necessary, and that most New Zealanders "would find it reassuring that the police are out there keeping a watch on the whole community".

"I wonder if she made those comments before thinking it through. I hope so."

She agreed with Green MP Keith Locke that Ms Collins should launch an inquiry into the SIG.

"Peace and environmental protesters are the conscience of society, not enemies of the state. The police should not be infiltrating such groups, spying on their every activity, and creating distrust between their members," Mr Locke said.

"It also means that scarce police resources are being diverted away from combating the really dangerous people -- such as those in the criminal gangs."

Ms Rees said she thought Mr Gilchrist was being paid to spy when she found a number of e-mails with no subject matter being forwarded to addresses.

"I was disgusted. I thought he shared common values with me, which was one reason why I was in a relationship with him," she said.

"I thought it might have been private investigators rather than police at first, but once I found he had also been sending information on fascist groups as well I thought it must be police, and I was able to confirm it by the next day."

Police did not return calls to NZPA.

Mr Gilchrist helped arrange protests and had become friends with many campaigners.

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

Mr Gilchrist told the newspaper that he'd been approached by police in the late 1990s after he lost his job and joined a beneficiary rights group in Christchurch.

He had been selective about what he told police, who paid him a "pitiful" amount, and did not think his friends were security threats.

"I called it quits many times. Then they'd call me in and by the end of the meeting I wasn't what you'd call energised, but I kept going," he said.

Earlier this year, Mr Gilchrist told the newspaper that Thompson and Clark Investigations (TCIL), an investigations company employed by Solid Energy, offered him money for information about anti-mining group Save Happy Valley Coalition.

That was a year after the Government ordered Solid Energy not to use paid informants, following TCIL's payments to student Ryan Paterson-Rouse to infiltrate the coalition.