The "corporate takeover epidemic" is threatening the economic health of the nation and should be stopped by congressional action, the AFL-CIO's 35-member executive council said yesterday.

The 13-million-member federation's governing body also denounced what it called the Reagan administration's "help-the-rich" farm policies, calling for a moratorium on farm foreclosures and a limitation of income-support aid to family farms rather than agribusinesses.

At its quarterly meeting here, the AFL-CIO council said that workers, consumers and communities are often the "ultimate losers" in takeover battles, and that tax laws and securities laws, which now encourage corporate raiding, should be changed.

The takeover issue has become important to unions because such mergers often result in demands for union concessions, abrogation of labor contracts, and financial drain on employers who are then less able to compete, labor officials said.

"The billions of dollars used to finance, as well as to fend off, takeovers is money that is not available for strengthening the national economy," the federation said. "The time, effort and imagination that corporate managers are devoting to waging and combating takeover battles is time, effort and imagination siphoned off from the task of building better products and providing better services at a better price."

The takeover frenzy, the unions said, is also encouraging the damaging tendency of many companies to maximize short-term profit and scrimp on research and development and long-term economic health.

"When the takeover succeeds, corporate concentration is increased; in the media the results threaten freedom of the press, and in the oil industry reduced competition has left consumers at the mercy of a few conglomerates," the AFL-CIO said.

Stockholders' rights should be strengthened so that they can have greater say in deciding whether companies launch or fend off takeover attempts, the statement said.