Japan threatened to leave the International Whaling Commission last night after anti-whaling nations voted to impose an explicit duty to conserve whales on the body for first time since it was founded nearly 60 years ago.
The "Berlin initiative", requiring the commission to set up a committee with a clear conservation agenda far wider than the body has previously pursued, was carried by 25 votes to 20.
Japan, Norway, Iceland and several Caribbean states opposed the resolution which they said transformed the commission's original purpose from conserving whales in order to use them sustainably, to conserving them for conservation's sake.
Japanese and European pro-whaling groups raised the possibility that they would withdraw from the organisation and run a commercial whale cull outside the IWC treaty.
Andres Rosenthal, the Mexican commissioner and one of the chief architects of the resolution, said it was as significant a day as when the global moratorium on whaling was agreed in 1986.
"In this very sterile debate we have been having for years it lays to rest the idea that the IWC is just about the resumption of commercial whaling," he said.
"It is a great day for those who want to save the whales. The world's whales can swim in peace a little longer."
The new committee is likely to consider, for example, the accidental killing by fishermen of 300,000 whales, porpoises and dolphins a year and what can be done to reduce this.
Masayuki Komatsu, the Japanese commissioner, said as he left the meeting: "I feel very resentful and angry about what has happened.
"The convention was created for the sustainable use of abundant resources. We know there are millions of minke sperm and sei whales out there.
"We will deeply consider whether to leave when the commission meeting ends."