Utah's top federal prosecutor advised Congress Wednesday to get tough on obscene "dial-a-porn" purveyors and to crack down on obscenity on cable and subscription TV.

U.S. Attorney Brent D. Ward said in a statement before the Senate Judiciary Committee that President Reagan's proposed anti-pornography law would prohibit for the first time the broadcast of obscenity by cable and subscription television.Ward, the chairman of a committee of U.S. attorneys concerning child pornography, obscenity and organized crime, said if the bill is passed, it would "give us the capability of prosecuting obscenity in this form (cable and subscription TV) as we currently prosecute obscenity in the form of printed matter, movies and video cassettes."

He said the bill would strengthen existing federal law by making obscene dial-a-porn a felony, rather than only a misdemeanor offense. Sexually indecent calls, rather than obscene ones, would remain a misdemeanor.

"I speak to you now as the only U.S. attorney so far to attempt to prosecute a dial-a-porn company," Ward said in his prepared remarks. "The fact that I have been alone in bringing such prosecutions, however, is not so much a sign of disinterest by the Department of Justice as it is a sign that the law has been inadequate."

A recent attempt to cure the inadequacy was passage of the Helms-Bliley bill, recently signed by President Reagan.

"However, even Helms-Bliley is seriously deficient in one important aspect," he said. "Under this law, obscene dial-a-porn messages will be punishable only as misdemeanors."

A misdemeanor can carry a jail term of no more than a year, whereas all serious crimes are felonies, with potentially much more severe punishment.

When the Helms-Bliley bill was studied by Congress, the Justice Department strongly urged that dial-a-porn be punishable as a felony, he said.

Ward said that in the experience of federal prosecutors, misdemeanor sentences - even when accompanied by substantial fines - aren't strong enough to deter the lucrative pornography industry.

He told the senators that pornography is a $6 billion to $8 billion industry in the United Sates, and Americans are in the middle of "heated competition among mega-scale enterprises engaged in the crass exploitation of human sexuality."

Ward said that in the past, obscenity was confined to seedy theaters and bookstores. "Today it is as close as the telephone, the VCR and the personal computer."

According to an appeals court, more than 7,900 calls can be connected to a single dial-a-porn telephone number, he said.

"In 1985 the number of calls ran between 6 million and 7 million per month," on New York lines. These calls yielded about $130,000 in monthly gross revenue, with little overhead, he said.

"With profits so high the risk of misdemeanor prosecution is easy to take. Furthermore, I know that U.S. attorneys will be more apt to prosecute these offenses if they know that the substantial effort required to do so will result in felony convictions and an increased likelihood of meaningful punishment and genuine deterrence."