New Zealand Cat Foundation chairman Anne Batley-Burton told the Herald she was concerned about the proposed policy.
She said while she was pleased to hear cats in urban areas wouldn't be targeted, she questioned how the council would define "high-biodiversity-value sites".
"If they include reserves and parks this could still be a huge concern. Imagine if the Rose Gardens, the Domain or the Ayr Street Reserve were to be included, and the problems that would arise if cats were being picked up and put down if they happened to wander into those areas?"
Brown said high-biodiversity-value sites included sites of special ecological interest or significant native ecosystems such as the Hunua Ranges or parts of Great Barrier Island.
It wouldn't include highly modified parkland like the Parnell Rose Garden or Auckland Domain.
However, it is yet to be decided if suburbs backing on to bush like the North Shore's Chatswood Reserve fit the definition.
"Chatswood Reserve does have some significant ecological areas on it, and we'd have to look into it further, but there is nothing proposed there for now or in the imminent future.
"We would never start pest cat control at a new site without letting the community know first."
Currently cats in New Zealand do not require a microchip by law.