The Federal Opposition has accused the Government of secretly ditching any possibility of taking Japan to court over whaling.

Opposition environment spokesman Greg Hunt says there is no money in the federal budget for the court case.

Mr Hunt says it shows the Prime Minister's election promise to take strong action against whaling was hollow.

"A bit of sunrise rhetoric from the Prime Minister which is dropped before sunset," he said.

"The budget papers - which are a test of a Government's seriousness - have dropped all money for a case against Japan.

"The budget papers have dropped all reference to a case against Japan in the purpose, the intention, the goal of our marine mammal conservation program."

Mr Hunt says Prime Minister Kevin Rudd has misled the public.

"This is a Government which has used rhetoric to imply that it was serious about whaling," he said.

"But in the cool light of day, there's no money in the budget, there's no reference to a case against Japan in the budget."

However, a spokesman for Environment Minister Peter Garrett says the Government remains committed to the issue.

He says the Government is trying to resolve the issue diplomatically, but funding will be made available if legal action is needed.