The ABC's Four Corners television program says it has evidence Japan has been using aid money to buy the votes of small Caribbean and Pacific island nations for a return to commercial whaling.
Environmental groups have long claimed Japan has been using aid funds to buy votes at the International Whaling Commission , or IWC, but Japan has always denied the charge.
Four Corners spoke to the Solomon Islands fisheries department head, Tione Bugotu, who claimed Japan poured money into the country in exchange for its IWC vote and cheap access to tuna.
The Solomons voted for a return to commercial whaling at this month's IWC meeting in Korea despite promising Australia it would either abstain or vote against Japan's proposals.
A politician in Dominica in the Caribbean, Atherton Martin, says Japan had told his government there would be no more aid without its vote.
Mr Martin told the programme that this is the high end of public sector extortion.