Two Japanese organisations have filed a lawsuit against anti-whaling group the Sea Shepherd Conservation Society, saying their crew and vessels are in danger.
The Institute of Cetacean Research and Kyodo Senpaku Kaisha are seeking a court order in the United States because they say Sea Shepherd's actions are becoming increasingly violent.
The Japanese organisations say they want the court to establish clear legal boundaries between peaceful protest and what they call illegal and violent sabotage.
A spokesperson Gavin Carter says the anti-whaling group has resorted to violent acts and has injured several Kyodo Senpaku Kaisha crew members, as well as damaging vessels.
"You'll get a situation where one of these attacks happens and someone will get so seriously injured or possibly killed, or you'll get vessels that are so badly damaged that it causes highly dangerous situations at sea," he says.
However, Sea Shepherd founder Paul Watson says the lawsuit will not deter the group from trying to save as many whales as possible.
He says it is the Japanese whalers who pose the greatest danger and the legal action is frivolous.
"We go down there trying to do what we do, taking every precaution that we don't injure them. They're down there trying to kill us," he says.
Mr Watson says any objective look at the evidence will show the Japanese have been extremely violent in their dealings with his group.