Labour is convinced John Key might be swayed by an online petition against commercial whaling.

Foreign affairs spokesman Chris Carter has launched the petition on his own web page, in the belief that public pressure is the only way to stop the Government from agreeing to a resumption of commercial whaling.

Mr Carter says the Prime Minister has showed in the past he is sensitive to public opinion.

"I think that the National/ACT Government has miscalculated New Zealanders' view about commercial whaling. I think there's a huge hue and cry over it. And I think if the public get a chance for their voices to be heard there's a very good chance the Government will back away from the proposal."

Mr Carter says he decided to act after being inundated with numerous calls from people wanting to know what they could do.

"People want to save our whales. They know they're an endangered species. And so the petition is a vehicle for the public to send a message to Mr Key and Mr McCully the Foreign Minister that Kiwis don't support commercial whaling."