Television New Zealand is apologising to viewers for being duped into running a fake interview with a man pretending to support the hunting of whales.
On TV1's Breakfast programme on Tuesday morning, it says, a young man named Jay Pryor came onto the show purporting to be a supporter of commercial whaling.
TVNZ says he had created a false name and a false website as part of the prank, and was photographed with the Prime Minister, who was also in the studio at the time.
It says Breakfast is reviewing its procedures and has advised the Prime Minister's department of the incident.
The same story appeared in the Sunday News newspaper.