The federal Equal Employment Opportunity Commission has charged that the Maryland legislature's administrative branch here has followed "a pattern and practice of excluding blacks because of their race" from its professional and clerical jobs.

The EEOC is charging that the state Department of Legislative Reference, which provides supporting services for the General Assembly, violated civil rights laws by trying to limit the number of blacks who applied for certan jobs, by not hiring blacks who applied and by failing to promote one black professional who works in the department's code revision division.

Federal officials investigated the department's hiring practices after the professional, Ralph Hughes, filed a complaint with the EEOC last July alleging that he had been disriminated against.

EEOC officials in Baltimore, after several months of investigation, made finding that Hughe's complaint was justified and further charged that department officials retaliated against Hughes for filing the EEOC complaint.

The five-page finding, distributed last week, asks the state to join with Hughes and the EEOC in settlement discussions. If the state fails to comply with the request, the EEOC could forward its finding to the Justice Department, which would then decide whether to file suit.

Robert Zarnoch, an assistant state attorney general who is handling the case for Legislative Reference, said yesterday that the department had not yet replied to the EEOC request. "Obviously, we disagree with the findings," Zarnoch said.

Legislative Reference officials said yesterday they had no comment on the case. Hughes also refused to comment because "the matter is still pending."

State legislators said yesterday that since Hughes filed his complaint, the Legislative Reference department has increased its efforts to hire blacks and recruited five black attorneys for jobs during this year's assembly session.

However, black legislature leaders said they were distrubed by the EEOC finding, which charged that until recently, the department excluded black lawyers from its analyst positions. It went on to note that while the legislature hires 90 to 100 persons during each session to work as proofreaders, messengers, and clerks, none of those employed has been black.

In one case, the EEOC finding says, the code revision division of the department -- where Hughes was employed -- attempted to limit black applicants for a legislative analyist job advertised in July and August of last year.

Sources said the EEOC received evidence that the responsibility for advertising for the position was assigned to a white staff assistant, even though Hughes was supposed to be in charge of job advertising.

According to sources, EEOC investigators received sworn testimony that when the white staff members asked why Hughes had not been told to advertise the job, a white manager in the code revision division responded, "we don't want too many of Ralph's friends to apply."

The finding says that the code revision division discriminated against Hughes, a legislative analyst making $26,000 a year, by failing to designate him in six years as a supervisor in his field, even though seven white analysts who were promoted to his classification during 1978-9 were almost immediately designated as supervisors.

The supervisory positions carry no additional pay, but are a necessary step to promotion to a higher salary level, Hughes alleged to the EEOC.

Further, the finding charges that code revision division managers retailiated against Hughes after he filed his complaint by giving him an unsatisfactory performance appraisal without justification.

"There is reasonable cause to believe," the finding concludes, "that [the department] has engaged in unlawfuel employment practices in violation of the Civil Rights Act . . . by refusing to promote [Hughes], retaliating against him and by failing and refusing to hire blacks as a class because of their race."