Britain and New Zealand are appealing to international whaling regulators to ban electric lances that are used to kill whales.
But Japan - the only nation to use electric shock weapons - insists the lances are the best method, not the cruelest.The Japanese delegation to the annual conference is asking for further research before the lance is phased out.
The commission called a worldwide moratorium on commercial whaling in 1986 to protect dwindling species, but a scientific provision allows the killing of a limited number of whales for research purposes.
Japan, which prizes whales for food, killed more than 400 minke whales this year for scientific research and has angered other nations by hunting within an Antarctic whale sanctuary. Minke whales are not an endangered species, and their numbers are reported to have greatly recovered since the moratorium.
Britain and New Zealand argue that the electric lance has a current far too low to kill such a large animal outright and only inflicts suffering.
British delegate Helen McLachlan, senior scientific officer of the Royal Society for The Prevention of Cruelty to Animals, said the lance "is an extremely cruel method of killing and must be banned."
Japanese delegates say the electric lance is the best method to shorten the killing time after the whale is harpooned and is superior to other methods. They base their claim on evidence from more than 1,000 samples.
The 39-member commission, meets until Friday in this northeastern seaport.