WASHINGTON (AP) _ The Federal Trade Commission charged Tuesday that the makers of a widely advertised series of diet plans engaged in false and misleading advertising.

Television, direct mail and print ads for the so-called ''rotation'' diet programs contained false, misleading and unsubstantiated claims, said the commission.

The FTC filed charges seeking to halt the ads by six firms doing a national mail-order business in the diets.

Named in the complaint were Buckingham Productions, Inc., of Doylestown, Pa., which does business as Rotation Diet Center; and Furlong-Elliot Corp., Freedom Center Inc., Plaza Business Services, N.F. Rotation Inc., and Rotation-Freedom Diet Inc., all of Furlong, Pa.

Telephone directory information in Doylestown and Furlong had no current listings for the firms, and calls to five telephone numbers listed in their ads resulted in recordings stating that the lines had been disconnected.

In addition to the charges against the firms and their operators, the FTC reported that it had obtained a consent agreement with Dr. Barry Bricklin, a specialist in the psychology of dieting, who settled charges that he had provided false and misleading endorsements for the diet plans.

Under the agreement, Bricklin is banned from future representations that consumers can eat as much as they want and still lose weight, and he is prohibited from making claims about usual or average weight losses.

That agreeement settles charges that Bricklin endorsed the diet plan by representing that he had tested the program, while he knew or should have known that the claims were false and misleading.

Under the rotation diet programs, consumers were advised that they could eat all they wanted for four days and still lose weight if they followed a severely restricted diet for the other three days of the week, while taking the company's vitamin supplements and wafers, the FTC reported.

The ads claimed a monthly weight loss of eight to 20 pounds for women and 12 to 25 pounds for men, the commission said.

The FTC charged that the company had no substantiation for these claims and also asserted that testimonials attributed to users of the diet were not genuine.

In addition to television, radio and direct mail, national advertising for the diet plans has appeared in such major publications as Family Circle, Woman's Day, T.V. Guide, Redbook, Family Weekly, Playgirl, the Chicago Tribune, the National Enquirer, the New York Daily News, Newsday and other newspapers, the commission reported.