Greenpeace is calling for a ban on plastic drink bottles, in response to dangerous levels of microplastics being found around Bay of Plenty moana.
Waikato University Master of Science student Anita Lewis found the particles in every sediment sample she took across the region.
Greenpeace Aotearoa said particularly high levels were found inside shellfish, including tuatua, cockles and wedge shells.
The environmental group said the government's plan to phase out what it calls "difficult to recycle single-use plastic items" does not go far enough.
Greenpeace plastics campaigner Juressa Lee said single-use plastic drink bottles from the likes of Coca-Cola and Pepsi, which are recyclable, should also be banned.