"I'm singing the Battle Hymn of the Republic all day. The truth goes marching on," Cambridge Mayor Alfred E. Vellucci said at a press conference yesterday. Though Vellucci may have lost his $16,000-a-year state job this week, he has still kept his sense of humor. And his title--he hopes.

Following allegations by The Boston Globe that he worked "irregular" hours for the state Department of Corporations and Taxation, Vellucci resigned his job there Thursday. He said, "I want to flatly say I did not get booted out of the tax department. I resigned on my own free will."

Owen L. Clarke, commissioner of the tax department, said yesterday Vellucci's statement was not totally accurate. "The fact is he resigned and the fact is the inquiry was going on" about the Globe's allegations, Clarke said.

Vellucci said he had been planning to retire for several months and distributed copies of letters to several state boards and insurance companies supporting his claim.

But Vellucci was quick to say he has no plans to retire from the Cambridge City Council, and that he plans a vigorous campaign for this November's election. Every two years the city council elects one of its members as mayor.

Peter Vellucci, the mayor's son and campaign manager, said yesterday about the allegations, "We feel it definitely has hurt us." He said most callers in the past few days have expressed their support, but the news media has been giving the charges extensive coverage.

"I've never done anything wrong in my life," Vellucci said yesterday. Several Cambridge political and community activists said yesterday they would not nominate him for the college of cardinals, but most said they sympathized with him.

City Councilor Francis H. Duehay '55 said the Globe article was unclear whether Vellucci took continual leaves of absence, which are permissible by state law, or whether he had a "no-show" position.

Victor Docouto, executive director of the Cambridge Organization of Portuguese Americans, said the weekly Portuguese newspapers will not be able to carry the story until next week and then they might give it little or no attention.

However, a Portuguese community leader said "Portuguese votes have put him over the top" in all elections but now "the people will [probably] wake-up."

Peter R. Lange, professor of Government and president of the Cambridge Civic Association, said even a small shift of support can be fatal under Cambridge's proportional voting system.

Vellucci finished seventh in a race for the nine council seats in 1975.

Vellucci's quick retirement may be the best indicator of the importance of the allegations. It was apparently the only way to blunt further publicity and Peter Vellucci said it will allow his father to expand his campaign commitments.

And his father underlined that point. "Now I can devote all my time to the people of Cambridge."