An RNZAF Orion has reported seeing a Spanish-owned blacklisted fishing boat during a patrol in the Southern Ocean.
The vessel, called the Bigaro, was spotted on Tuesday.
The New Zealand Government has called on Spain to take action against its owners as the vessel is blacklisted for illegal, unreported and unregulated fishing in Antarctic waters.
Foreign Minister Murray McCully says illegal toothfish fishing in the Southern Ocean is a scourge, destroying fish stocks and killing thousands of seabirds, including albatrosses.
He says governments cannot turn a blind eye to this.