After years of "gritting teeth" while Marvin Mandel held press conference defaming his work, federal prosecutor Barnet D.Skolnik broke his self-imposed silence and went on television yesterday to insure that "the public does not believe all that vile nonsense."

The "nonsense" he attacked included Mandel's accusations that the governor and his codefendants were prosecuted for political reasons, that Mandel was convicted on filmsy charges and that he, Skolnik, had a personal vendetta against Mandel. TR AD ONE

"It disturbs me, frankly, when people say . . . like the governor and his friends, say that there was no evidence," Skolnik said. "Something must have convinced 12 people, none of whom I know -- none of whom had any relationship to anybody in the case -- unanimously beyond a reasonable doubt that a crime was committed."

For a decade Skolnik has been the chief federal prosecutor in Baltimore, responsible with his colleagues for the successful prosecution of former Vice President Spiro T.Agnew, two county executives and now Mandel. It is work. Skolnik asserted, that requires the faith of the public and "their belief in the integrity of our work."

Since the conviction of Mandel and his five codefendants last August, there have been pulished attacks on Skolnik's prosecution of the case. And last Friday codefendant Irvin Kovens claimed Skolnik should be prosecuted for tax evasion, a charge the prosecutor later said was "ridiculous horse apples . . . It isn't worth discussing it."

The heart of the public controversy is the application of mail-fraud and racketeering charges in a case that is essentially about bribery. The three assistant U.S. attorneys prosecuting the case -- Skolnik, Ronald S.Liebman and Daniel J.Hurson -- chose to use the mail-fraud statutes because bribery didn't "go far enough . . . for the bribes, payoffs, fraudulent and phony cover-ups," Skolnik said.

Although Skolnik spent most of the 30-minute program discussing his philosophy of crime and its deterrence - repeating his belief that there will always be criminals - he did admit to one hitherto unknown ambition: He said he might consider becoming a journalist.

When asked if that wasn't a sarcastic remark, Skolnik said, no, he was serious. "I'm not sure about television, though, I'm not sure I'm pretty enough."

But the appeal of television to Skolnik theh criticized prosecutor proved irresistible.

"I thought that if I went on television, in all my cute, triple-chinned adorableness, I could say, 'Here I am, this is how we do our thing and don't believe all that other crap,'" Skolnik said in a separate interview yesterday.

The 36-year-old prosecutor was most temperate when trying to measure the effectiveness of his work. He hasn't changed the system, Skolnik said, rechanged the system, Skolnik said, remarking that it would be absurd to think he could.

"We hope, frankly we think, though, these prosecutions have a deterring effect," he said.

For the man that he and his colleagues are sending to prison, Skolnik showed little public sympathy. Mandel, the prosecutor noted, is spending twice as much on housing as Skolnik does, hardly the sign of someone crippled by bankruptcy. But that is not the point, he said.

"I can't play God," he said. "If we gather evidence showing criminal activity, it would be a violation of our job not to prosecute just because the consequence of a successful prosecution would be devastating to someone."

He refuted, at some length, charges that his office leaked information to the press. Besides the fact that it is wrong to do so. Skolnik said, it would have presented "potentially tremendous legal hassels for us."

And he laughed at the rumors of political conspiracy being behind the presecution by just shaking his head, and saying no, that is not what his job is about.

Some people will forever think that Mandel was innocent, unfairly hounded out of office, Skolnik said. "But I hope and anticipate that most objective citizens won't believe that. He is a convicted felon."