Environment Minister Nick Smith has laid a complaint with police alleging protesters rubbed rat poison over his face and clothes at the Nelson market.

The Nelson MP has welcomed a drop of poison bait at the Brook Waimarama Sanctuary near Nelson on Saturday. It's being dropped to kill predators and protect native birdlife but there is local opposition to it and three people were arrested there on Saturday.

Dr Smith said a couple attacked him at the Nelson market on Sunday. They left once police were called but continued with threats to poison his family.

"The situation became quite frightening when it escalated from verbal abuse and throwing rat poison at myself and volunteers to physical shoving and rubbing rat poison over my face and clothes."


He said he was tolerant of peaceful protesters but the incident went too far and he lodged a formal complaint.

"The incident was disappointing because people are generally respectful at the Nelson market even when they disagree with government policy or my views.

"This incident at the Nelson market comes on the top of deliberate sabotage of the sanctuary fence and the holing of a fuel tank on site for helicopters."

He says the Brook Valley Community Group opposing the pest control needs to condemn these criminal acts.

"This matter has been to court three times, twice in the High Court and a third in the Court of Appeal. The courts have ruled clearly that the pest control operation is lawful.

The regulation and monitoring of the poison is tight and the environmental benefit of a pest-free sanctuary is huge," Dr Smith said.

He said the science was clear that the only way birds like kiwi, kokako, kea and kaka would survive was to effectively control the pests that decimated their populations.

A total of 26.5 tonnes of bait laced with brodifacoum will be dropped in the operation, according to a court judgment.