Beginning late this summer, a set of rather extraordinary commercials will begin to appear on television sets across the nation.

"Listerine will not prevent colds or sore throats or lessen their severity," the announcer's voice will say.

The commercial is the end product of a seven-year battle between the Federal Trade Commission and Warner-Lambert Co., of Morris Plains, N.J., maker of Listerine, which has been advertised and sold as a cold remedy since 1921.

FTC officials say they are closed to issuing a final order in the case, which the agency finally won when, after a long court battle, the Supreme Court upheld an FTC claim that advertising for Listerine was deceptive.

Listerine, the best-selling mouthwash in the country, had advertised that it stopped colds by killing the bacteria that cause them and that garling with Listerine resulted in fewer and milder colds.

FTC studies have shown that no gargle is effective against colds, which were shown to be caused not by bacteria but by viruses that enter through the nose and eyes.

The FTC usually settles false-advertising cases by merely stopping the ad campaign. But it ruled that Listerine's campaign had been running so many years that many people would continue to believe the message even after the ads were taken off.

Consequently, the FTC has ordered that Warner-Lambert spend $10.2 million in "remedial advertising."

Warner-Lambert spokemen Thorn Kuhl told Associated Press yesterday that he expects the ads to begin appearing in August and September.

"We have been working on appropriate television commercials. We're just waiting for the final FTC order before we begin placing them," he said.