In a showman-styled twist to avoid Hatch Act violations, the city's Fire Fighters Association yesterday trotted out a nervous 11-year-old son of a fireman to read their endorsement of mayoral candidate Marion Barry and six City Council candidates.

Wearing a white-plastic "Honorary Fire Chief" helmet, Joseph A. Lawson III read the short statement that highlighted the dilemma faced by tens of thousands of District of Columbia residents banned from political activity.

In a voice barely audible over the sounds of passing trucks in front of Engine Company 2, Lawson said he was speaking on behalf of the firemen's local 35 union "due to the Hatch Act which prohibits District of Columbia employes from participating in partisan politics."

David A. Ryan, a city fireman and president of the union, said he was not able to read the endorsement because the association's lawyers said he would be in violation of the federal law. "The Hatch Act is just something that has to be repealed," said Ryan.

Ryan said he had collected almost $2,000 in voluntary contributions from the city's 1,400 firemen that will be distributed among all the endorsed candidates. Although the firemen are prohibited from working for the endorsed candidates, Ryan said, "their wives could" do volunteer work for them.

The Hatch Act prohibits partisan political activity of some 106,000 federal employes and slightly over half of 40,000 District of Columbia employes who reside in the city.

Campaign managers for two of the principal mayoral candidates. City Council Chairman Sterling Tucker and Mayor Walter E. Washington, stressed yesterday that they knew of no "Hatched" federal and city employes working in their campaigns.

A third, Barry's campaign manager Ivanhoe Donaldson, said, "I am sure there are a number of people who are supposedly Hatched who are working for him."

Reporters covering the campaign, however, have repeatedly run into a number of civil servants who are close to the candidates at small meetings, fund-raisers and forums for all the candidates. When questioned, all of the employes said they did not interpret their activities as partisan politics.

"I'm just here as a citizen," smiled Rodney Coleman, executive assistant to Tucker on the council and a Capitol Hill resident, at a recent Foxhall Road, NW Ward 3 Democratic Committee forum at Mount Vernon College. He felt with Tucker.

Deidre Daily, a council aide to Barry and wearing a "Marion Barry for Mayor" campaign button, said she was also not involved in politics as she was interupted collecting signatures at a fund-raiser for Barry at Shepherd Park in upper Northwest Washington.

"The Hatch Act says I can do what I want to except collect money and hold an official position in Barry's campaign," Daily responded. "I can do what I want in off hours."

When Mayor Washington made a recent tour of discos he was followed by his aides, James (Jimmy) Jones, director of the Youth Advocacy Office; Lewis M. Anthony, a staff assistant to the mayor, and Carol Payne, another of the mayor's assistants.

They mayor's wife, Bennetta, special assistant to the assistant secretary for employment and training at the Labor Department, and Barry's wife, Effi, a health inspector with the city's Department of Environmental Services, have made numerous campaign appearances with their husbands. Tucker's wife, Alloyce, is active in civic affairs but does not work.

At a Georgetown fund-raiser Monday, Bennetta Washington made an allusion to her status as a "Hatched" federal employe. "I'm a peculiar animal in Washington," said Mrs. Washington about her inability to campaign overtly for her husband. Nonetheless, she said she could get up and talk about the mayor "in a family way."

Barry, when asked about his wife's campaign speeches in his behalf, said, "Effi is just speaking as my wife. You're going to tell me a wife cannot speak for her husband?"

Enacted in 1939, the Hatch Act was passed to correct alleged abuse of the federal civil service system that arose with the growth of the federal bureaucracy during the New Deal. It prohibits all partisan political activity by both federal and District of Columbia employes.

Philippe Neff, a senior attorney with the Civil Service Commission, said the law exempts only city employes who work for an independent candidate for political office. For either a Democratic or Republican candidate, Neff added, federal and city employes "can't even lick a stamp."

Violations of the act, not a criminal offense, can be punished by suspension or firing. There were 800 investigations of violations made across the country last year but action was taken in only 12 cases. "The rest washed out," said Neff.