A full-page ad in a British newspaper criticising the New Zealand dairy industry is a "form of economic sabotage", the Prime Minister says.
Animal rights group SAFE took out the $10,000 ad in The Guardian criticising the alleged abuse of bobby calves in New Zealand.
It shows a glass of milk mixed with blood and an embryonic-like calf inside, saying the industry is "contaminated with cruelty".
The organisation, along with Farmwatch, released undercover video last week of bobby calves being mistreated and had threatened to take it global.
At his post-Cabinet news conference yesterday, John Key said he was "disappointed".
"I think it's a form of economic sabotage. They're quite entitled to make the claims they make on the basis they can back them up," he said.
"If you were to take an ad in New Zealand at least you can make the case you're trying to influence lawmakers in New Zealand and the New Zealand public; to take an ad in the international media, for what end is that other than to try and stop international consumers buying our products? I can't see how that's a fair thing to do or an appropriate thing to do."
Anyone with information on alleged ill-treatment of the young male calves should make it public and the Government will investigate.
Mr Key believed sales could be damaged by the ad because the industry's image is important.
The vast majority of those in the dairy industry care about their animals and their welfare, he said, and the few who don't should be punished accordingly.
There are mixed views over what damage the ad could do, with University of Canterbury marketing lecturer Ekant Veer believing it unlikely there'll be a huge backlash.
However, University of Auckland senior marketing lecturer Mike Lee said the industry would need to do some damage control and do it quickly to reassure the world the images shown are a minority.