THEY SAY Chairman Michael Pertschuk has the Federal Trade Commission, like Leacock's famous horseman, galloping madly off in all directions.

They say he promises more than he can possibly deliver, starts more than he can possibly finish, generally tampers with American lives in a period of reaction against government regulation.

Mobil Corp. even ran an ad, the fable of King Sam the Avuncular, which, after two columns of elephantine irony, arrived at this moral: "Nothing cripples innovation and enterprise like heavy-handed regulation."

Somewhat to his own surprise, Pertschuk rather enjoys all this combat and adrenalin. In his 15 years as counsel and then staff director for the Senate Commerce Committee his job was to avoid just that sort of thing.

"I'd love to take credit for all the strong things the FTC has done," he said, "but when I saw a list of nine current projects we have [ranging from children's TV ads to used car inspections, from Hertz refunds to Levi jean prices, from dishwashers to dogfood], I began adding it up and I found that seven of those projects were started before I ever got here. I'm happy to take credit for things we've completed."

So much for the scattergun accusation.

"We're under a lot of criticism on the Hill for doing too much. Some congressmen say the public doesn't want this now. But the polls say just the opposite. In one major survey in '77, 15 percent said the government is doing too much and 36 percent said not enough.The same survey in '78 showed only 10 percent felt it was too much and 42 percent said we should do even more than we are."

So much for the supposed temper of the people.

As for Mobil, Pertschuk replied with a fable of his own charging that it is the big, conservative corporations themselves that seek government regulation in the first place, as a means of stamping out competition. His fable features an interestingly named character, Sir Barely Mobile, who himself had in fact "petitioned most piously for the regulation of foreign imports...."

In the eye of the hurrican at FTC, all is quiet, Pertschuk ambles into his office balancing a piece of cake on his palm: the staff is celebrating somebody's birthday. He sprawls on his sofa and breathes a glow back into his moribund cigar.

There was some valid criticism of the agency in the Nader report and the bar association report in the '60s," he remarks. "But they neglected the fact that we did some good stuff, too. Getting the cigarette ads off TV: that was pretty radical. "We're also under fire from Congress a lot. Now, I'm a creature of Congress, professionally, and I've got a lot or respect and affection for the members. The problem is the nature of the things they hear from a skewed segment of the society, from organized groups with plenty of resources. The chambers of commerce. On the other hand, we're blessed by a good press. I don't mean flattery. What we do makes news."

His basic purpose, he says, is to give the consumers the information and let them make their own decisions.

"We don't substitute our judgment for theirs. We're not paternalistic. We want to make sure the system of competition actually works, so that they get a real choice."

This is why he is suspicious of business mergers by their very nature.

Not everyone agrees about who's making the judgments. In a ruling that upset government regulators everywhere, U.S. District Judge Gerhard Gesell recently barred Pertschuk from taking part in the "kidvid" commercials case because he had disqualified himself with his "emotional" statements on the subject.

The next thing you knew other groups were trying to take advantage of the precedent: the American Medical Association now hopes to keep the chairman, as his staff calls him, out of its attempt to prevent doctors from advertising.

One thing about the FTC - it deals in matters that affect us all every day, so there is bound to be weeping and gnashing of teeth whatever it does.

An attempt to curb the agency is being made in a proposal by which either house of Congress can nullify an FTC ruling by majority vote unless the other house acts affirmatively for the FTC.

This would seem to be an attack on the agency's basic strategy, which is to work through rules rather than lawsuits. For instance, in a sales operation where the salesmen work by commission, there is no incentive to keep the customer happy, to follow through on performance.

Instead of suing every time a consumer complains, the FTC simply enacts a rule requiring a pro-rata refund to unsatisfied customers.

The technique may be practical, but it also comes close to legislating, and some congressmen feel their function is being usurped.

"A friend on the Hill said it did seem we've gone about systematically alienating every leading citizen of every town in the country. It's just the nature of the agency that we've got to police virtually the whole economy. But I don't feel we scatter our shots or overreach. We pick our priorities carefully. We turn down a lot of things. I'm proud of our planning."

In fact, he adds, the FTC now has laid out its areas of concern and will break no new ground but will concentrate on what's already started.

This does not mean that anybody is breathing easier. The people who know Pertschuk, pro and con, agree he is a force to be dealt with.

"It's not just that he's smart as hell and relates easily and positively with people," said consumer specialist Lee White, an old friend. "He got some good schooling in the commerce committee, he saw how the real pros work. For instance, he'd never have his secretary call Commissioner X to his office. Instead, he'd walk down to the commissioner's office himself. Also, he's crafty enough not to go see people only when he needs them. Not that he's Machiavellian, just gregarious. And intelligent."

On the other hand, one longtime observer who didn't want his name used said that while he recognized Pertschuk's outstanding talents and ability" he nevertheless feels the man "has forgotten he's running an agency and is no longer on the Hill. He's projecting an image of legislator and policy-maker rather than regulator."

This person has suggested to Pertschuk that "he is talking endlessly about things he'll never do, and is polarizing everybody. He told a conference of investigative reporters to go out and investigate the conglomerates. Now, why does he do that? I ask him. He should talk about the good things the commission does, which far outweigh the negatives, and about his excellent staff and their very constructive attitude."

Such is Pertschuk's power that several adversaries wouldn't talk about him for publication. Unoffically, the consensus seemed to be that he is going beyond his mandate.

This message was relayed from the Kellogg Co. executive offices in Battle Creek, Mich.:

"The Kellogg Company has no comment whatsoever on Michael Pertschuk."

The chairman has encountered stifflipped silence before. It doesn't visibly faze him. Still, it must be comforting to have around him a crack staff, mostly handpicked (some of the best agency chiefs haven't been able to name their own people and suffer from it), and on two walls giant photo-collages by his second wife, Anna Sofaer, an artist who has exhibited in New York. (Her paper on a major archeological discovery she made in the Southwest is about to be published in a leading science magazine.)

Having a competent and supportive team helps, of course. But Pertschuk also has learned to take Washington on his own terms.

"No, I don't have a horrendous day My whole philosophy and sytle is to seek out good people, workaholics, and not hold them on a tight leash. People work better when given authority and some space. I avoid meetings as much as possible. There are those who hold meetings for the sake of holding meetings."

He gets up at 6, writes or studies for two hours at home, leaves the office at 6:30 p.m... He tries to take a swim at the Waterside Club before going home. He doesn't bring work home, doens't work on weekends, limits business parties to one night a week. He takes off all of August to read, think and write.

"Nader took me to task for that. Not because he didn't want me to take time out to think, he liked that part, but because he felt the staff eased up when I was gone. Well, he's wrong.You come by here any night at 10 and you'll see the lights on. My people work their tails off. They believe in what they're doing."

It takes a certain serenity to stick to that kind of schedule in this work-obsessed town, and maybe some hard experience. Pertschuk's first marriage cracked up partly because his life used to be so work-centered.

"This time the family really is first," he says. "We don't spend a lot of our social life with my colleagues. And Anna has her own separate life and colleagues."

At a Sunday reception recently he showed up in a sport shirt and brought along his son Mark, a senior at Oberlin, and one of Mark's friends. His daughter Amy is at Berkeley, learning mechanical drafting, and Anna's son Dan Sofaer, 10, lives at home.

A bit rumpled, a bit overweight, graying hair forever out of control, Pertschuk doesn't look his 46 years. He moves constantly, restlessly.

"The swimming is marvelous for me. I feel alive for three more hours in the evening. Never was much of a drinker, and we drink almost entirely wine. Sometimes if I have two glasses at dinner I get sleepy and it cuts into my evening, which is irritating."

One thing about Mike Pertschuk, according to people on both sides of the fence, is that if you ask him a question, he'll give you a real answer. He can be as wary as the next Washington lawyer (even among friends at the Ethical Society, where he called everyone by first name at a recent informal question session, he brought an aide with him), but at the same time there is a directness, a forthrightness - refreshing qualities in the land of obfuscation.

It goes back to his childhood in New York, where his father was a fur merchant.

"My father had a strong sense of fairness, and he took great pride that he had been chosen by his colleagues to be the arbiter among them. In a business where people play a lot of games, he had a reputation for integrity and telling the truth."

His father had a partner, a white Russian who dressed and spoke with studied elegance, and once when the man was on the phone it was apparent that he was being asked what price he had paid for a certain load of skins. He lied.

"I could see the red rise on my father's neck. When the guy got off the phone, my father pointed a finger at him and said, "Don't you ever do that to me again." I never forgot that."

There was also a civics teacher in high school, "Franklin Carter, a person of integrity," and Judge Gus Solomon in Portland, Ore., for whom he clerked. "He always told lawyers to deal from the top of the deck, and he was consistently harsher in sentencing people of means. He sent a lot of doctors and lawyers to jail."

Coming to Washington in 1960 as an assistant to Sen. Maurine B. Neuberger, Pertschuk landed in the midst of the Kennedy excitement just in time for the first blooming of the consumer issue. His first project with Neuberger was the cigarette ads. Two years later he went to the commerce committee where he was staff until named to lead the FTC in 1977.

"It's two years now, a testing time when some people start moving out. But I'm committed to the full seven years. Meanwhile, I'm a lawyer. We're an agency of lawyers, which is good because they're not on the same civil service status as most. You can demand performance of lawyers. You can move them around as well as out because a lawyer always has someplace to go."

On the other hand, lawyers do have this problem with language. Pertschuk harps on it all the time, to the point that some FTC documents have been quoted in magazines for their wit and verve and general stylishness.

In a speech about his former boss, Warren Magnuson, whom he admires immensely, Pertschuk cited a definition in an FTC proposal that went like this:

"Hearing aid - any wearable instrument or device designed for, offered for the purpose of, or represented as aiding persons with or compensating for impaired hearing."

Magnuson pounced on it. The new version:

"Hearing aids are instruments worn to improve one's hearing."

Pertschuk admits he is a frustrated writer. Words, their power and beauty, fascinate him. His skill with them comes from the same source as his skill in handling his critics: an instinct for the specific.

Once a congressman attacked the agency with a barrage of rhetoric, thundering at the climax, "What are you doing for the people of Worcester?"

Pertschuk got hold of a Worcester newspaper, found 15 ads showing the direct effects of what the FTC has done, pasted them up and mailed them off.

That was the last he heard of the matter. CAPTION: Picture 1, Pertschuk at FTC hearing in 1977: "We've got to police virtually the whole economy." Photo by Frank Johnston-The Washington Post; Picture 2, Michael Pertschuk in front of one of two photo-collages in his office done by his wife, Anna. Sofaer. Photo by Lucian Perkins for The Washington Post; Illustration, no caption, from Pertschuk's fable