Pro-whaling nations look set to command a majority of the votes when the International Whaling Commission (IWC) annual meeting begins on Friday.
Several countries which appear likely to vote with the pro-whaling bloc have joined the body in recent weeks.
UK marine affairs minister Ben Bradshaw said he is “very concerned”. A pro-whaling majority could lead to the scrapping of conservation and welfare programmes, though not a return to full-scale commercial whaling.
That would need three-quarters of the delegates to vote in favour, which is extremely unlikely.
But a simple majority would be enough to end IWC work on issues which Japan believes to be outside its remit, such as welfare and killing methods, whale-watching and anything concerning small cetaceans such as dolphins.
“For the first time since the 1970s, the IWC would be under the control of the whalers,” commented Vassily Papastavrou, a marine biologist working with the International Fund for Animal Welfare (Ifaw).
“Japan has said that it intends to undermine decisions which protect whales and stop the conservation work of the IWC,” he told the BBC News website.
The potential for collision is higher at this year’s meeting than it has been for decades.
Formed in 1946, the IWC’s original purpose was to regulate commercial whaling; and after it became obvious that some species were being depleted to the verge of extinction, that regulation took the most robust form possible: a global moratorium.
Norway made a formal objection to the ban and has continued to hunt, though catching radically fewer numbers than a century ago. Japan, and more recently Iceland, hunt under an IWC ruling which allows nations to catch whales for “scientific research”.
Both have stepped up the size of their annual hunts in recent years, with the 2006 catch on target to exceed 2,000, the largest take since the introduction of the moratorium in 1986.
Pro-whaling nations insist that a limited return to commercial hunting is possible; stocks of some species are high enough, they maintain, charging that the IWC has become an organisation dedicated to preventing whaling, contrary to its purpose.
At the IWC’s foundation is supposed to be sound science; arguments such as which stocks are sufficiently robust to hunt are in theory answered on a strict scientific basis.
But there are huge variations in estimates of minke whales, the species currently most hunted, which makes it almost impossible to set global catch limits.
The scientific process has also become mired in politics, with decade-long discussions on a mechanism called the Revised Management Scheme, designed to facilitate a return to limited commercial whaling, breaking down earlier this year.
The anti-whaling bloc is now led informally by Australia, New Zealand and Britain, with the US a major ally.
Within the last year this group has co-ordinated letters of diplomatic protest to Norway and Japan, signed by 12 and 17 countries respectively.
“They are losing the argument, internationally and domestically,” said Ben Bradshaw.
“None of the pro-whaling nations have markets for the meat; young Japanese, Icelanders and Norwegians don’t eat it, consumption is falling.”
This argument is countered by organisations supportive of whalers and whaling, such as Norway’s High North Alliance.
“We think there is growing support for whaling in principle and in practice,” said its secretary Rune Frovik.
“Whales belong to the animal kingdom. In some cultures they eat frogs, others don’t; Hindus don’t eat beef, that’s their choice, but they don’t try to prohibit the rest of the world from eating it.
“And we think that you can’t find anything more environmentally friendly than whale meat – this is an animal which lived in nature, we are harvesting nature’s surplus and you don’t have to destroy nature to do that.”