New Zealand Foreign Affairs Minister Murray McCully says someone could get killed in the Ross Sea if aggression between Japanese whalers and an environmental protest group continues.
Both sides blame each other for two collisions in the past two days.
A video taken by Japan's Institute of Cetacean Research on Friday and sent to Radio New Zealand shows the Sea Shepherd Conservation Society ship Steve Irwin ramming the Japanese whaler Yushin Maru 2 while under fire from water-cannon.
However, Sea Shepherd says it has video footage proving that the Steve Irwin did not deliberately ram the Yushin Maru 2.
The institute says the incident shows the extreme measures being used to frustrate whalers. But Steve Irwin captain Paul Watson says it's the Japanese who are at fault.
Mr Watson claims the Steve Irwin was caught between two Japanese ships and had no room to manoeuvre. He says the institute is violating several international treaties and Sea Shepherd is the only group willing to police its actions.
On the other hand, the institute says Sea Shepherd is using increasingly violent means to try and stop legitimate research activity.
Mr McCully says that while it's not clear who's responsible, it is clear that lives are being endangered.
Moreover, if someone gets hurt, he says, it would take rescuers a long time to reach them.
