Dunedin police door-knocked a Dunedin activist asking about their plans for the signing of the Trans-Pacific Partnership Agreement.

Scout Barbour Evans was visited by two police officers on Thursday morning, "asking me what I'll be doing for the TPPA events".

The officers said they were following a national directive and were "visiting all known activists in the country".

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Superintendent Christ Scahill, national manager response and operations said in a statement, "Police is responsible for all aspects of safety and security for the upcoming signing of the Trans-Pacific Partnership in Auckland".

"We will draw upon our extensive experience of policing a wide range of high profile events in recent years as part of our arrangements.

The police operation would be overseen by Police National Headquarters, and would involve staff from a number of police districts.

"Police will not discuss any operational details for the event, including staff numbers involved, as is standard for any matters involving security.

"We can however say that we plan for every eventuality which can be anticipated, and the measures we take will be appropriate and thorough.

"We will draw upon a range of resources to police the event, however normal police operations in districts will not be affected."

The police visiting known activists to ask their plans for the TPPA show appalling judgement and are a poor attempt at a chilling effect said Green Party Co-leader Metiria Turei.

"Having police show up at your door to ask you what you plan on doing is chilling and the police know that" said Turei.

"It carries with it an implicit threat and New Zealanders have the right to speak out and have their voices heard. Being an activist isn't a crime, being an activist is being passionate about something and last time I checked that wasn't illegal."

The 12-nation free trade agreement will be signed in Auckland on February 4.