A national police campaign to door-knock TPP activists is part of a larger trend of "chilling" opposition to the Government and the right to protest, a civil liberties lawyer says.
Police have been visiting "known activists" opposed to New Zealand's involvement in the Trans Pacific Partnership trade agreement ahead of protests planned in several cities tomorrow.
Lawyer Michael Bott said the tactic appeared to be part of "an increasing trend on the part of the police".
"They seem to be doing it proactively on behalf of the Government and its projects.
"It's worrying that New Zealand citizens who are concerned about the agreement suddenly find themselves the target of police.
"It has a chilling effect on freedom of expression and the right to protest.
"These people haven't committed any crime and yet the police are going to conduct a search or an interview, and there are legal concerns with that."
Mr Bott noted similar cases of police intervention.
"We saw it in the raid of the [Kim] Dotcom mansion, the police going in all guns blazing," he said.
"We've also seen it where people have been surveyed because of an alleged link with 1080 protesters, and a classic case in point is the 'teapot tapes' case where strong-arm tactics were used to threaten Mr [Bradley] Ambrose.
"And it was seen in the raid of Nicky Hager which was found to be unlawful - you can see the police behaving in a proactive way at the behest of the Government."
Scout Barbour-Evans, a Dunedin activist who goes by the gender-neutral pronoun "they", said an officer knocked on their door about 10am yesterday.
The officer wanted to know what the plans were for the anti-TPP protest in Dunedin, Scout said.
Scout compared the situation to the Springbok tour, saying the increased surveillance felt akin to 1981, particularly following the presence of armed police at Prime Minister John Key's State of the Nation speech on Wednesday.
Labour Party police spokesman Stuart Nash said he thought door-knocking was "not the way we do things in this country".
"My initial reaction is that it is a little heavy-handed. The protesters have a legal right to protest within the bounds of the law."
Green Party co-leader Metiria Turei said the tactics were "straight intimidation at the behest of the National Government".
New Zealand First leader Winston Peters said the police would need an explanation for their actions.
"The right to protest is one of our fundamental rights, legitimately protest, that is."
Anti-TPP protester Professor Jane Kelsey said the police monitoring was "entirely predictable" behaviour from the Government.
The approaches come days after police undertook mass riot training in anticipation of the agreement being signed in Auckland next week.
Meanwhile, Labour MP David Shearer is set to be censured for breaking the party line on the TPP after speaking out in support of it.
Labour leader Andrew Little would not comment.