More than 7000 people have signed a petition calling for school possum hunts to be banned, after it emerged baby possums were drowned at a fundraising event.

The Ministry of Primary of Industries is investigating claims at least one person at the event at Drury School last weekend was seen taking joeys from the mother possum's pouch and drowning them in a bucket of water.

Last Sunday's weigh-in - where the drownings occurred - came after several days of possum hunting, with hunters bringing the dead adult marsupials in for weighing, before they are sold to a fur buyer as part of a fundraising initiative.

The act was spied by environmentalist and education lecturer Lynley Tulloch, who has created the petition.

She says possum hunting events demonstrate an absolute lack of conscience "and in fact could be very damaging for children's growing sense of compassion and care for other animals."

Tulloch said one person has responded to her petition by saying possums are not animals, they are pests.

"It's that level of thinking which is actually at the heart of the problem here - the demonisation of the possum over time in New Zealand has become completely rampant."

An MPI spokeswoman confirmed it had received a complaint and were making inquiries to determine if an offence had been committed.

SAFE chief executive, Jasmijn de Boo said drowning was an unacceptable way to kill an animal.

Drowning newborn animals is considered particularly cruel because they have an automatic reflex to hold their breaths, meaning it takes longer for them to lose consciousness than if they inhaled water.