Confronted with an increasingly aggressive and successful campaign by conservationists to stop the hunting of whales, the world's remaining whaling nations have mounted a concerted counter-attack to try to save the shrinking industry.

Whaling has suffered both from its depletion of the world's whale population and the combined efforts of dozens of conservation groups who have joined together in publicity campaigns, economics boycotts, international lobbying and physical sabotage against the industry.

Led by Japan, the world's largest consumer of whale meat, the whaling interests have responded by hiring their own lobbyists and launching a propaganda counter-offensive. They also have organized to block attempts by other nations, including the United States, to imose a worldwide mortatorium on commercial whaling at this week's annual meeting of the International Whaling Commission here.

In fact, several Japanese organizations have engaged the help of former CIA director William Colby, now a Washington attorney, former transportation secretary Brock Adams and Washington lobbyist Robert J. Keefe to help fight their battles in Washington.

Until recently, conservationists had been optimistic about winning at least a temporary moratorium on commercial whaling while scientists studied more closely the danger that many kinds of whales, even the more numerous smaller species, have been hunted into near extinction.

The conservationists already have succeeded in creating an antiwhaling majority in the 24-nation commission by persuading some of its members to stop whaling and by packing the commission with nonwhaling nations, including this year's new members, Oman and Switzerland.

But Japan and other whaling nations from whom it imports whale meat have begun to fight back. A new London-based "Whaling Information Center" is publishing and distributing material defending whaling as a legitimate industry and an important part of Japanese culture.

The Tokyo-based Japan Whaling Association hired Keefe, a fund raiser for President Carter's reelection campaign, to combat the Carter administration's anticommercial whaling policies, according to conservationist Craig Van Note of Monitor, a Washington-based consortium of American antiwhaling groups. Because of the increasing restrictions and the relative scarcity of whales -- each of which is worth thousands of dollars for its meat, oil and skin -- the Japanese whaling industry now requires government subsidies to stay alive, though it still employs an estimated 50,000 persons.

Whaling also has become an international public-relations problem for Japan. Van Note said Colby registered with the Justice Department as a foreign agent for a Japanese lobbying group, the Center for Political Public Relations, to report on what the center calls Washington's "negative view of Japanese activities in the whaling industry."

Adams was hired by the Japanese fishing industry, according to Van Note, to protect its interests in the U.S. 200-mile fishing zone. One of Adams' clients, Van Note said, is Japan's giant Talyo Fishery Comany, which conservationists want banned from fishing in U.S. waters for alleged importing from outlaw whalers.

Although no group has claimed responsibility, militant conservationists appear to have struck directly against "outlaw" whalers by sinking three of their ships earlier this year with explosives while they were docked in Spanish and Portuguese harbors.

Representatives of the Japan Whaling Association at the whaling commission meeting here insist they are making certain that Japan imports only from whaling commission member nations. But conservationists claim that much of this whale meat still comes from hunting over commission quotas or from nonmember Taiwan shipping to Japan through whaling commission member South Korea. Taiwan applied to join the commission this year, but its application has been held up because only two present members -- South Korea and South -- formally recognize it as a nation.

Japan organized a rump meeting here last week of the seven whaling countries in the 24-nation commission -- itself, the Soviet Union, South Korea, Spain, Peru, Brazil and Iceland.

This otherwise unlikely coalition was formed to counter unfair and unscientific influence on the whaling commission by "extreme antiwhaling propaganda and pressures," according to a statement by the group's provisional chairman, Shigeru Hasui of the Japan Whaling Association.

The whaling nations claim there are still plenty of smaller whales in the world's oceans. Conservationists complain that imprecise estimates have overestimated the populations of endangered whale species in the past, and that without a whaling ban many will become extinct.