Australia saysit has no plans to send a vessel to monitor the escalating situation some 1,300 nautical miles south of Tasmania, urging both sides to show restraint.
"It's critical for safety at sea to be the highest priority and for absolute and utmost restraint to be exercised by all parties in this very remote and inhospitable region," Environment Minister Peter Garrett said.
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WATCH the dramatic collision - as filmed by conservationists
Sea Shepherd captain Paul Watson has accused the Japanese of a hit and run over the crash, which saw the Japanese ship Shonan Maru crash into the high-tech Ady Gil trimaran.
"The Shonan Maru suddenly started up and deliberately rammed the Ady Gil, ripping eight feet of the bow of the vessel completely off," a Sea Shepherd statement said. "The Ady Gil is believed to be sinking."
But the Japanese Fisheries Agency said the Ady Gil came abnormally close to the Shonan Maru and suddenly slowed down while crossing in front of it.
Whalers accused of 'hit-and-run'
"These acts of sabotage that threaten our country's whaling ships and crew were extremely dangerous," it said in a statement. "It is totally unforgivable."
Watson insists that while it may not be possible to salvage the futuristic $1.5m craft, the Sea Shepherd organisation won't abandon its campaign.
Videos released by both the Japanese and the activists show the sleek, black powerboat and the Shonan Maru colliding as the whaling ship targets it with water cannons.
All six of the Ady Gil's crew, who had earlier hurled stink bombs at the whalers to disrupt their annual hunt, were rescued by Sea Shepherd's Bob Barker ship. One suffered two broken ribs.
There was no major damage to the Japanese ship and no Japanese crew members were injured in the collision, the fisheries agency said.
The whalers accused the Ady Gil's five New Zealand and one Dutch crew of trying to tangle the Nisshin Maru's rudder and propeller with rope, and aiming a "green laser device" at its sailors, as well as launching stink bombs.
'Violent extremism' claim
"The Sea Shepherd extremism is becoming more violent... Their actions are nothing but felonious behaviour," Japan's Institute of Cetacean Research said in a statement.
Sea Shepherd activists have harassed the Japanese fleet over the past six hunting seasons and claim to have saved the lives of hundreds of whales.
Watson said the annual pursuit had now turned into a "real whale war".
"The Japanese whalers have now escalated this conflict very violently," he said.
"If they think that our remaining two ships will retreat from the Southern Ocean Whale Sanctuary in the face of their extremism, they will be mistaken.
"We now have a real whale war on our hands and we have no intention of retreating."
