IT'S HARD to imagine a less likely wellspring of controversy than The Dial, a fancy-shmancy program guide being published by four public TV stations, including Washington's WETA. The magazine is as quaint as a tea cozy at granny's house and innocuous beyond belief.

But its existence and the fact that it accepts paid commercial advertising has made it a subject of unjustly heated debate in such remote locales as the house of Representatives. Most of the ruckus has been kicked up by Philip Merrill, publisher of The Washingtonian, a magazine of considerable expendability itself but which Merrill claims will suffer unfail losses in ad sales at the hands of The Dial.

He has asked for and, incredibly, received, the help of the U.S. Congress in safeguarding his profits.

Among the tomatoes thrown at the magazine, mostly at Merrill's urging, was a ludicrous last-minute amendment to a public TV appropriations bill in the House. The amendment bars federal funding of any public TV or radio station which carries adds in its program guide, even if it's a two-watt station in Cornhusk, Iowa, and desperately needs the revenues.

Ward Chamberlin, president of WETA, says public broadcasting is now trying to convince senators not to include the amendment in the Senate version of the bill, which may come to a vote this week or be delayed until after the November elections.

In addition, the magazine's publishers (who also include stations in New York, Los Angeles and Chicago) recently lost a bid to mail the publication at cheaper, non-profit, second-class rates. That boosts expenses by more than $50,000 an issue. Chamberlin says the ruling is being appealed and that the post office will refund the money if the decision is reversed.

"All we're asking is to be treated the same as The Smithsonian, college magazines, blinkety-blinkety-blink and other not-for-profit magazines are treated," Chamberlin says. "If they want to change those rules, fine, but don't make special rules for us."

Chamberlin insists that no federal money has been used to publish The Dial and that, contrary to a Merrill allegation, Dial ad salesmen are not on the WETA payroll.

Obviously the foes of The Dial, for whatever private interests, are using an ion cannon to snuff a gnat. But the publication of The Dial does point up a major problem facing public TV stations. Underfunded for years, and with Uncle Sam refusing to play Daddy Warbucks to the hilt, they're almost forced to become more and more commercial in the perennial scrounge for cash.

It's been said the United States spends proportionately less on its public television system than does any other civilized, televisionized country in the world.

Strapped for funds, public TV edges closer and closer to the commercial system it shouldn't be emulating. During the last great orgy of money-begging and tote-bagging on public TV stations in August, a number of stellar attractions used to lure viewers were actually programs previously seen on commercial TV. These included an inadequate peek at TV in the '50s shown several years ago by NBC.

Then there was the CBS Playhouse 90 classic, "Requiem for a Heavyweight," a deserved encore to be sure but more rudely interrupted with spiels on some public TV stations than it was when CBS showed it back in 1957. On Maryland stations, there were nearly 20 minutes of pitch time inserted into the program -- far more than on vulgar old commercial TV.

And then to make matters worse, the pitchers come on screen and tell you how lucky you are you don't have to sit through commercials. Even Chamberlin refers to this money-raising tactic as "beating our membership over the head all the time."

In recent years, public TV stations have behaved like commercial stations in other ways. Norman Lear's "Mary Hartman, Mary Hartman" was sold for broadcast on a public, not commercial, station in Miami, Fla. Chicago's WTTW, one of The Dial publishers, is exhuming for broadcast reruns of the CBS cast-off, "The Paper Chase."

The year, when Rep. Lionel Van Deerlin (D-Calif.) and staff were trying, unsuccessfully, to rewrite the 42-year-old Communications Act, it was proposed that public TV stations be allowed to accept commercials, as long as they were grouped and relatively unobtrusive. The rewrite bit the dust, but the idea remains alive. It's extremely likely that commercials will find their way onto public TV in the future.

As for The Dial, its highfalutin contents suggest it might better have been named The Dull. The articles are not exactly in the can't-put-down class; but the ads are more revealing about the public TV audience, or what it's imagined to be like. Advertisers in the first issue include Tiffnay's, Cuisinart, Saks Fifth Avenue, Merrill Lynch, E.F. Hutton, Bloomingdale's, Dewar's White Label, Old Grand-Dad and a 12-year-old Scotch. Presumably, those who don't drink 12-year-old Scotch and don't shop at Tiffany's can always watch icky commercial TV.

It's hard if not impossible to sympathize with Merrill, a man on a self-serving rampage that has no constructive aspects. But the propriety of a commercial enterprise on behalf of federally funded TV stations is also open to question. The management of WETA has hardly done a spectacular job of running a television station, so why should they be branching out into magazines?

On the other hand, if public TV were adequately endowed in the first place, ideas like The Dial might never have had to face either the light of day or the rocket's red glare of an enraged publisher with, it appears, awfully good friends on The Hill.