A federal appeals court yesterday ordered the Federal Communications Commission to reconsider a deregulation of children's television advertising that critics charge has turned many cartoon shows into little more than extended commercials.

The U.S. Court of Appeals for the District of Columbia ruled that the FCC had "failed sufficiently" to explain why it lifted the guidelines limiting the amount of commercials that could be shown on children's TV shows to 16 minutes an hour.

Elimination of the guidelines in 1983 spawned a new species of children's programs: cartoon action shows based on popular toys, games, candy and breakfast food, often produced by the product manufacturers themselves. Critics charged that the shows made it difficult for children to distinguish between entertainment and commercials.

"Our review of the FCC's actions in this case fails to unearth a 'reasonable basis' adequate to justify the FCC's termination of the children's commercialization guidelines," the three-judge panel ruled in a decision written by Kenneth H. Starr. "As the agency has seen it, kids are different; the commission cannot now cavalierly revoke its special policy for youngsters without re-examining its earlier conclusions."

Yesterday's decision immediately set off a debate between Action for Children's Television, the consumer-advocacy group that filed the suit, and the FCC.

ACT suggested that the court's action could lead to major changes in children's television programming by forcing the FCC to redefine the line between entertainment and commercials. "We're going to see the end of program-length commercials, we're going to see the end of children being fair game for toy-budget promotions that are disguised as children's programming," said Peggy Charren, head of Boston-based ACT. She added that the decision "gives a big message to broadcasters and the toy industry that they've had it when it comes to using kids."

FCC General Counsel Diane Killory said the court had not specifically attacked the FCC's policy on children's television, but only the way in which the policy was made.

"I think what it means is that the task before the commission, if it wants to eliminate the guidelines, is to provide the elaboration that the court asks," Killory said. "The commission really needs to explain itself better."

She said the commission would meet to review its earlier ruling, and said the FCC did not necessarily have to hold new hearings into the matter.

The FCC eliminated the guidelines on commercial time in children's programming during a period when it was lifting many regulations covering television. The commission said at the time that it felt that market forces would control the commerciality of children's shows, just as they do for adult programming.

The 1983 decision reversed what had been a hardline position by the FCC on children's commercials. During the 1970s, it had repeatedly expressed concern about the number of commercials being shown children, and in 1974, the commission published a report that said children are "far more trusting of and vulnerable to commercial 'pitches' than are adults." In particular, it said, young children "cannot distinguish conceptually between programming and advertising."

In its ruling yesterday, the appeals court said, "For almost 15 years, the FCC's regulation of children's television was founded on the premise that the television marketplace does not function adequately when children make up the audience. . . . "

"The commission has offered neither facts nor analysis to the effect that its earlier concerns over market failure were overemphasized, misguided, outdated or just downright incorrect," the court said. "Instead, without explanation, the commission has suddenly embraced what had theretofore been an unthinkable bureaucratic conclusion that the market did in fact operate to restrain the commercial content of children's television. To make matters worse, this latter-day inspiration is barely articulated, much less explained."

"The reason that the FCC got zapped by the courts is that it conducted this business in the back room," Charren said yesterday. "It's been an outrageous aberration in the way TV serves the public."

She said she believes the current members of the commission, led by Chairman Dennis Patrick, might be more amenable to regulating children's television than the commission was under former chairman Mark Fowler.

"It seems to me that this is the perfect case to say, 'Well, we went too far here,' " Charren said. "I think it's perfectly appropriate for the commission to say, 'Hey, maybe we made a mistake in this one. Everybody was too greedy, and it didn't work.' "

Killory declined to speculate on what the commission might do. Executives for several television networks and toy manufacturers either declined comment on the decision or could not be reached.

In a related matter, the court ruled that the FCC had not overstepped its bounds when it relaxed rules requiring television stations to keep comprehensive programming logs. The issue was raised by ACT in its children's-programming suit, but the court said it could "discern no flaw" in the FCC's decision on logbooks.