Australia threatened Japan with further legal action against its whale hunt in the Antarctic, while New Zealand held an international protest on Monday.
Japan started an expedition last Tuesday to catch up to 333 minke whales in the Antarctic.
"We are working with other like-minded nations to build international consensus against Japanese whaling," Australian Foreign Minister Julie Bishop said in a statement.
"We are also exploring options for further legal action."
The International Whaling Commission banned commercial whaling in 1986, but Japan has continued hunting whales for what it calls scientific experiments, although whale meat is seen even in school lunches.
In 2010, Australia filed a lawsuit -to which New Zealand also joined later- with the International Court of Justice (ICJ) against Japanese whaling in the Antarctic.
The ICJ ruled last year that the hunts were not scientific, forcing Tokyo to revise its Antarctic whaling programme.
Japan's Commissioner to the International Whaling Commission Joji Morishita said that “...we are now confident that we completed the scientific homework as well as we are now meeting the ICJ judgment requirement.”
However Australia says that lethal research is unnecessary.
"The science is clear: all information necessary for management and conservation of whales can be obtained through non-lethal methods," Bishop said.
Together with New Zealand, as well as 31 other countries, they are the biggest opponent of Japan’s yearly whale hunt.
New Zealand also said it would press for an end to "this outdated practice."
Prime Minister John Key said that New Zealand's ambassador to Tokyo delivered a "strong" formal message from 33 countries, including the United States and Australia, Mexico, South Africa and EU member countries, to Japan.
"We consider that there is no scientific basis for the slaughter of whales and strongly urge the government of Japan not to allow it to go ahead," Key said in a statement.