Foot and mouth disease contamination is possible from such imports, he says.
"The risks are high and we should take no chances," O'Connor says.
A decision on what will happen to the ship is due in days, Radio New Zealand reports.
In August Greenpeace NZ welcomed a decision by state-owned farm manager Landcorp to stop using PKE.
"Greenpeace has been campaigning for seven years for a phase-out of PKE on New Zealand farms, due to its role in both tropical rainforest destruction and industrial dairying" said Grant Rosoman from Greenpeace.
PKE is a by-product of the palm oil industry, which is the leading cause of rainforest destruction in Indonesia.
New Zealand is currently the largest importer of PKE, using about a quarter of the world's supply each year as supplementary feed for livestock. On some farms, it's believed to make up nearly 50 per cent of cows' diets, Greenpeace has said.