A British anti-whaling protester was detained on board a Japanese harpoon ship last night after storming the vessel in an attempt to scupper Japan’s controversial whale hunt.

Giles Lane, 35, and an Australian activist, Benjamin Potts, 28, members of the militant environmental group Sea Shepherd, were held after throwing acid bombs and ropes to forcibly board the Yushin Maru No 2, Japanese officials said.

Colleagues on board Sea Shepherd’s Steve Irwin flagship claimed that the pair had been taken hostage, beaten and tied to a railing, a claim vehemently denied by the Japanese. However, photographs show Mr Potts tied up with a rope and tethered to railings along the ship’s deck.

“Any accusations that we have tied them up or assaulted them are completely untrue,” said Minoru Morimoto, chief of the government-backed Institute for Cetacean Research. “They are in custody while decisions are made on their future.”

The Foreign and Commonwealth Office said that it would take up the issue with the Japanese Government. Japan later released photographs of the two men, unbound, on the bridge.

Paul Watson, the captain of the Steve Irwin, said that he considered the two activists to be hostages when the Japanese ship sailed off two hours after the confrontation with the men still on board. The high-seas confrontation came amid a day of rising tensions over Japan’s highly controversial whale hunt in the Southern Ocean.

Commercial whaling has been banned worldwide since 1966 but Japan conducts an annual minke and fin whale hunt in what it describes as scientific research. Japan says that it must kill whales to study them and that it then sells the meat, which is allowed under International Whaling Commission rules. Its fleet plans to land about 900 whales, most of which will end up on Japanese dining tables — evidence, say the activists, of the true commercial nature of the Japanese enterprise.

Hours before the confrontation, an Australian court had declared Japan’s annual whale catch illegal and ordered the whaling fleet to leave the hunting grounds of the Antarctic. Australian activists called on Kevin Rudd, the country’s anti-whaling new Prime Minister, to enforce an injunction against the hunt inside Australia’s exclusive economic zone, which Canberra claims extends 200 nautical miles from Australian-declared territory in Antarctica.

Late last night Stephen Smith, the Australian Foreign Minister, said that Japan had agreed to release the two activists, but there was no confirmation from Tokyo.

The incident followed a prolonged cat-and-mouse chase between the Japanese whaling fleet and a growing flotilla of vessels determined to prevent what they see as Japan’s illegal hunt. Ships chartered by Greenpeace claimed on Monday that they had chased several Japanese vessels away from the hunting zone, including the so-called factory ship on which the whales are carved up and processed.

Greenpeace, which refuses to cooperate with Sea Shepherd, adheres to a non-violent ethos of blocking whaling activities, chasing whaling ships from their hunting grounds or sending boats out between ships and whales.

Sea Shepherd claims to have sunk up to ten ships in its efforts to disrupt the whale hunt, prompting Japan to denounce its members as terrorists.

Times Recommends

• Tehran cannot live up to its rhetoric
• The new unicycle that will ‘change the world’
• We cannot wish away Iran’s bomb