Japan has used funds from its tsunami recovery budget to subsidize its controversial annual whaling program, environmental activists say.
Greenpeace says 2.3bn yen ($30m; £19m) is being used to fund extra security measures for the whaling fleet.
Japanese officials argued when they applied for extra funding that whaling helped coastal communities.
The whaling fleet reportedly headed for Antarctic waters this week, though Tokyo has not confirmed the reports.
There has been a ban on commercial whaling for 25 years, but Japan catches about 1,000 whales each year in what it says is a scientific research program.
Critics say those claims are just a cover for a commercial operation, and accuse the Japanese of hunting the animals to the brink of extinction only for food.
Activists from the Sea Shepherd group have attacked the fleet as part of their campaign against whaling.
The Australian and New Zealand governments have both criticized Japan’s decision to continue whaling.
They are both considering sending vessels to monitor the whaling fleet.
Sea Shepherd activists have promised to carry on their campaign against the whaling fleet.