The head of the Justice Department's Antitrust Division warned Maryland yesterday that its proposed rules restricting lawyer advertising fail to meet guidelines set by the Supreme Court.

"The proposed rules are from every perspective unnecessarily restrictive," Assistant Attorney General John H. Shenefield wrote to the Maryland Court of Appeals' Standing Committee on Rules, which drafted the proposed advertising rules.

"In fact," continued Shenefield, "they would appear to prohibit the very advertising which the Supreme Court constitutionally protected" in a landmark decision last June. He accused the committee that drafted the rules of misreading "the entire thrust" of the Supreme Court decision.

In his letter Shenefield attacked the makeup of the Maryland court's rules committee, most of whose members are practicing attorneys, for having a conflict of interest on the issue because their "commercial and economic interests may be directly affected by any recommendations they may make."

A provision of the proposal to which the Justice Department official especially objected would allow lawyer advertising only of maximum fees for sevices instead of the minimum fees that were specifically approved by the Supreme Court.

The rules committee said this restriction was put in to stop lawyers from using "bait and switch" tactics, but Shenefield said "the approach adopted seems wholly out of proportion to any conceivable problem that may arise in this area.

"It, in fact, would operate to deny consumers access to meaningful information, and would have the likely effect of discouraging advertising of specific fees by making such advertising impractical.

"An important objective of advertising," he continued, "is to let the consumer know that a product or service is available at a price the consumer will find attractive. Advertising only maximum fees woule be inconsistent with that objective."

The Court of Appeals, which bears sole responsibility for regulating the practice of law in Maryland, will hold a unique public hearing on the advertising restrictions next Thursday. This is the first time in the state's history - and one of the few times in the nation - that nonlawyers have been given a chance to influence directly the way lawyers practice their profession.

Shenefield's letter was submitted as a comment on the proposed rules, released earlier this month, which still must be approved by the Court of Appreals.

While state regulations governing lawyer advertising do not usually fall within the authority of the federal government. Shenefield's letter carries unusual weight since he is in charge of the Justice Department's Antitrust Division, which already has challenged the American Bar Association's restrictions on lawyer advertising.

Shenefield's letter was low-key and couched in lawyer-like language, but his chief deputy, Joe Sims, was more direct in a speech two weeks ago at New York University Law School. He said restrictions such as Maryland's on lawyer advertising are likely to result in more Supreme Court decisions against the organized bar.

In his letter, Shenefield urged the court not to give that committee, which it appointed, undue weight in its consideration of lawyer advertising rules because of its conflict of interest.

He wrote that " . . . The sincerity and wholly honorable intentions of the members of the practing bar," is assumed. But, "their determinations are entitled to weight equivalent to their inherent persuasiveness and on more. This court must insure that the various public interests involved in the regulations of lawyer advertising in Maryland are given full consideration and appropriate weight before acting upon the proposed new rules."

Legal reformers maintain that allowing lawyers to advertise will help bring down the cost of legal services - especially such routine matters as simple wills, uncontested divorces and uncomplicated property settlements.

There are indications already that advertising has helped lower legal costs. In New York, for instance, some lawyers' fees for uncontested divorces have gone down from more than $750 to between $150 and $250 since the Supreme Court ruled that lawyers could advertise.

The Supreme Court ruling concerned a legal clinic in Phoenix that advertised cut-rate legal services in order to attract middle and low-income clients who could not afford fees usually charged by lawyers.

Ronald Sharrow, a partner in the Baltimore based legal clinic of Cawley Schmidt & Sharrow, complained that the proposed Maryland rules are "so restrictive as to not make it worth advertising at all. We can't reach the right people with the type of advertising we'd have to put in."

Shenefield, in his letter to the Maryland court, echoed many of Sharrow's complaints.

The Justice Department officials opposed another requirement that would force lawyers who advertise fees to supply written notices that clients are entitled to itemized, regular bills.

These rules, Shenefield said, would end up "seriously reducing the incentive lawyers may have to advertise their fees by substantially increasing the practical problems involved in such advertising."

He added that the written disclosure rule could just as well apply to all lawyers - whether they advertise fees or not.

"It makes little sense." Shenefield said, "to adopt rules that absolutely guarantee that no one will be misled or otherwise injured by legal advertising if those rules have the practical effect of making it prohibitively burdensome for lawyers to engage in legitimate advertising."

He also attacked the proposed rule banning lawyers advertising on radio and television, the sources of information to a large segment of the nation's low-income population. Even the ABA's suggested regulations - which Shenefield also found too restrictive under the Supreme Court guidelines - allowed radio advertising and left TV advertising up in the air.