Key Points:

The Security Intelligence Service has been spying on an MP's private life and his communications with constituents, he says.

Green MP Keith Locke, a former peace activist, applied under the Privacy Act to have his top-secret security file released - revealing what he describes as distasteful intrusion into his personal life and unacceptable intrusion into the democratic process.

The declassified file showed that he had previously been covertly photographed, that the SIS had kept track of his private work with constituents and that he had been monitored in other ways as late as 2006.

He is demanding assurances that the monitoring will not continue, and calling for tighter Government control and public accountability for the so-called spooks. "Clearly the SIS has been operating without adequate government oversight," he said.

Both Prime Minister John Key and his predecessor, Helen Clark, said they were never told that the SIS was spying on MPs.

John Key said he had not authorised any surveillance warrant or investigation into a sitting MP. "There would need to be demonstrable evidence any individual presented a security risk before I would issue a warrant," he added.

Warrants to mount covert surveillance operations, like phone bugging, are overseen by Sir John Jeffries, the Commissioner of Security Warrants.

Last night, the SIS issued a statement saying it was "not actively" investigating any sitting MP. It acknowledged that some recorded information might have been very personal and sensitive - including convictions, adoptions, personal finances, physical and mental health - and said that would not be disclosed.

"The practices of the NZSIS that are reflected in some of the personal files are of a different era," the statement said. "They were meticulous in detail and often contained material that would not be collected today."

Locke is the son of prominent environmentalists and Communist Party members Jack and Elsie Locke - they were reportedly described by former Prime Minister Robert Muldoon as the most notorious Communist family in the country.

Some of the 400-plus documents in Locke's security file date back to when he was 11 years old.

Keith Locke joined the Socialist Action League in 1970. He was too radical for Labour, which tried to expel him in 1974. He joined the Greens and in 1999 he entered Parliament. He campaigned strongly against New Zealand's imprisonment of Algerian dissident Ahmed Zaoui, which was supported by the SIS.

Green Party co-leader Jeanette Fitzsimons said such surveillance of Locke would be a "huge discredit" to the SIS.

"MPs are elected by the people. To have the secret service spying on them is hugely anti-democratic," she said.

Fitzsimons and Maori Party MP Hone Harawira will both be requesting their SIS files.

Harawira said he had been subjected to SIS surveillance as a member of the protest movement, before entering Parliament, and had once spotted his file while in police custody - alleging that he had been involved in an arms deal on a boat in Whangaparaoa Harbour.

Green MP Sue Bradford said she had been spied on by the police's criminal intelligence branch and had her phone tapped while she was involved with the Unemployed Workers Rights Centre. She did not know whether the SIS had also spied on her.

"I remember coming back from the shops with my husband and children, unpacking the shopping and looking up and seeing two guys with a camera filming us. It was quite extraordinary; it led us to believe we were being spied on in our private lives."

Veteran anti-apartheid and human rights campaigner John Minto claimed the SIS "wouldn't hesitate" to spy on a serving MP. " It's very worrying. These people (SIS) are simply above the law and the democratic process. They see politicians as being meddlers."

Former Labour leader Helen Clark, Prime Minister for almost all of Locke's Parliamentary career, said she had no knowledge of the SIS spying on Locke or any other MP.

* Oops! Not so secret activities

In 1981, the SIS was criticised for drawing up a list of 20 "subversives" involved in protests against the Springbok Tour.

The same year an SIS operative mistakenly left a briefcase containing sandwiches, a Listener magazine and a diary on a journalist's fence in Wellington.

In 1996, two agents broke into the home of anti-free trade activist Aziz Choudry. He was awarded an out-of-court settlement and a Crown apology.

In 2002, the SIS certified Algerian asylum-seeker Ahmed Zaoui a security risk. After a legal challenge to the certificate's reliability, he was allowed to stay in New Zealand.

Hone Harawira, now a Maori Party MP, was once arrested and secured by plastic wrist ties to a scaffold with fellow protesters . But the protesters moved the scaffold to read their files while police were away. His contained allegations he had done an arms deal on a boat in Whangaparaoa Harbour.