Green Party MP Keith Locke has announced he will retire at this year's election.

Mr Locke, 66, said it was time to move on to new projects, but that he would be working hard until the election.

"The National Government can't relax just yet," he said.

"I will keep up the political pace right through to the election. The Search and Surveillance Bill and the SIS Amendment Bill will not have an easy ride through Parliament, and I will keep campaigning for my Bill of Rights Amendment Bill as well as for the withdrawal of SAS troops from Afghanistan."

Mr Locke, who has been in Parliament since 1999, has been a persistent critic of secrecy in New Zealand intelligence services and military involvement in Afghanistan.

He still labels the Communications Security Bureau base at Waihopai an 'American base' and accused the New Zealand SIS of spying on MPs when it was revealed they kept a file on him.

A long-standing campaign against increasingly strict security laws had been his proudest achievement in Parliament, he said.

"We're not as bad as Australia or Britain where the surveillance state is a lot more prominent. That's a special achievement.

"I'll probably be remembered as the MP who most strongly resisted legislation inspired by the 'war on terror' which has eroded our civil liberties.

"Perhaps my efforts mean that our anti-terrorism and security laws are not so draconian as they are in some other Western countries."

He is also proud of his five-year parliamentary campaign to get detained Algerian asylum seeker Ahmed Zaoui residency in New Zealand.

"I was there from the first week he was imprisoned. To see him finally freed was perhaps my biggest single achievement."

Age and the rise of new politicians in the Green Party were factors in his decision to retire after four terms, he said.

He has seen an overhaul of the party's MPs since he entered Parliament in 1999, with prominent departures including former leader Jeannette Fitzsimons and outspoken former representative Sue Bradford.

"I'm getting on a bit. It's time to move on. I didn't really want to be here at age 70 still starting new projects.

"It was an interesting road in those early years. All of us were pretty well known for our campaigning. The new MPs haven't had the national reputation before they came into politics. I think you're seeing them gaining that reputation now."

He plans to use his time away from parliament writing a history of the Green movement in New Zealand and internationally.

"Even when I am not operating from a parliamentary platform, those who start wars and abuse human rights will not escape my attention."