A city permit examiner pleaded guilty yesterday in federal court here to soliciting and accepting bribes from three persons seeking building renovation permits in return for lowering permit fees or assisting the applicants in other ways.

The examiner, Warner B. Jenkins, 48, who has been fired from his $24,527-a-year job as a structural engineer with the Building and Zoning Regulation Administration, was indicted last November on charges of soliciting or accepting payments--ranging from $20 and a fifth of liquor to $1,900--from 23 persons between September 1980 and May 1981.

Jenkins, who had pleaded not guilty in previous court appearances and denied the allegations in an interview with The Washington Post last June, told U.S. District Court Judge Aubrey E. Robinson Jr. yesterday that he had solicited and accepted bribes on three occasions.

Assistant U.S. Attorney Harry R. Benner told Robinson that in return for the guilty plea, the remaining charges against Jenkins would be dropped. Each of the counts carries a maximum penalty of 15 years in prison and a $20,000 fine. Robinson did not set a date for sentencing.

The investigation into Jenkins' activities began after an article in The Post last June 4 reported that three persons said Jenkins solicited bribes from them in return for lowering the fees they would have to pay the city for their permits. The fees are based on the total cost of the renovation to be done.

Those three persons were listed in the indictment, but Jenkins pleaded guilty to soliciting and accepting money from only one of them--Brian Fitzpatrick, who went to obtain a permit for renovation of his Capitol Hill row house on Nov. 13, 1980. Fitzpatrick estimated the value of the work at $30,000. Jenkins, in return for a $250 check from Fitzpatrick, lowered to estimate to $3,000, reducing the permit fee by more than $1,000.

Prosecutor Benner yesterday gave details of the other two illegal payments that Jenkins admitted accepting. Benner said that on the same day Jenkins took the bribe from Fitzpatrick, he took a $600 check from Robert Brooks, an employe of Builders Hardware Corp. in Rockville, which was providing new doors for a condominium conversion project in Northwest Washington, Benner said.

The original plans for the project called for doors with a higher fire protection rating than the 60 doors Builders Hardware supplied, Benner said. Brooks asked Jenkins to permit the lower-rated doors to be substituted, but Jenkins refused to approve the change, even though the substitute doors actually meet code requirements.

Jenkins then called Brooks and asked "How much would it be worth?" to permit the substitution, Benner said. Jenkins told Brooks that he would allow the substitution in return for $600, which Brooks then paid, Benner said.

Jenkins also pleaded guilty to issuing a fraudulent permit on Feb. 26, 1981, to a real estate broker arranging for construction of a planned Hardee's fast food restaurant at 1634 I St. NW. The broker, Norman Busada, gave Jenkins $200 in cash and a $650 check in return for a permit that Jenkins, who was not supposed to have permits in his possession, typed up and gave to Busada. Benner said neither the permit nor the money went through the department's regular accounting procedures.

Jenkins, although a relatively low-level GS 11 employe, was one of three persons in the BZRA who regularly set the permit fees and approved building plans for all renovation projects in the District.

D.C. architects, builders and contractors interviewed for The Post's initial story last year said the city's system was so lax in its review procedures that projects are routinely undervalued, depriving the city government over the last 20 years of millions of dollars in fees.

Mayor Marion Barry, acting after the June allegations about Jenkins, said a preliminary city study showed that some projects had been undervalued by 30 to 50 percent, and ordered city officials to start strict enforcement of building permit rules immediately.

City officials said they then altered procedures so that no applications for permits may be altered without approval by senior agency officials, and tightened control over blank permits.

One city official said recently that since Barry's order it appears the city has collected substantially more in renovation fees per project. City officials estimated that the city last year collected about $1.5 million from such fees.