Ms Irvine, who said the coffee cups and lid claims were misleading, was keen to clear up confusion about the lids, which were becoming "more and more" common.
What added to the confusion was that PLA cups, made of a fibrous material, were compostable in household compost bins, just not the lids.
If the PLA product looked like plastic, like the lids, it could not be composted in New Zealand, and there were currently no recycling options either, Irvine said. PLA cups belonged in the landfill.
Packaging companies argued councils should set up facilities where PLA cups could be composted, but such a move was "not going to happen" because of the logistical problems in sorting them and the length of time it took to compost them.
She believed the companies were guilty of "green-washing" their products.
The best option for coffee lovers was to take a commuter cup, which at some cafes meant they could get a discount.
"Any single-use product is a waste of resources."