Preventing child pornography has become such a popular cause that bills to outlaw it have been introduced in 23 state legislatures and Congress this term.

In the House, where more than 25 per cent of the members have joined to cosponsor the "Child Abuse Prevention Act," hearings are set today and Wednesday before the Crime Subcommittee of the Judiciary Committee.

And the House Select Education Subcommittee plans hearings in New York, Los Angeles and here, starting May 27.

In the Senate, two similar measures have been introduced, cosponsored by 20 senators.

At present, no federal stature prohibits recruiting children for pornography or filming and producing of child porn material.

Children as young as 3 have been used in films and magazines, ranging from soft pron poses to explicit sexual acts. Recent national publicity has resulted in widespread crackdowns on child porn sales but Justice Department officials say it is still available under the counter in many of the nation's adult bookstores.

And most of the crackdowns have had to rely on obscenity laws, which pose First Amendment problems for prosecutors.

The child abuse prevention bill introduced by Reps. Dale E. Kildee (D-Mich.) and John M. Murphy (D-N.Y.) calls for up to 20 years' imprisonment and or a $50,000 fine for producing pornography involving children or knowkingly permitting a child under 16 to be photographed in sexual acts or simulated sexual acts. This includes nudity if such nudity is for the purpose of sexual stimulation.

The bill also carries a sentence of up to 15 years and/or a $25,000 fine for shipping or selling such materials. This second part of the bill has caused some concern among civil libertarians.

The American Civil Liberties Union supports prosecuting those producing the material but does not support prosection of distributors and sellers, arguing this opens the door to further censorship.

However, law enforcement officials and groups lobbying for child pron legislation argue that the only way to reach the producer and the recruiter of children is by imposing stiff penalties on the more visible distributors the children being filmed, rather than touching the obscenity question, in hopes of avoiding any First Amendment conflict.

The number of runaway children exploited for pornography and prostitution is estimated in the thousands. Several cases uncovered this year revealed that parents, often posing for pornography themselves, allowed their children to be used in porn films.

The films are only an adjunct to sexual abuse, often incest, according to members of Odyssey House, a New York city drug rehabilitation and child abuse center. They estimate 44 per cent of the females they treat report a history of incest.

Legitimate film makers, too, have at times stepped into the area of child porn and some scenes in present-day legitimate films would be prohibited by such federal legislation as the Kildee-Murphy bill.

For example, some of the scenes of Jody Foster playing child prostitute in "Taxi Driver" and the sub-teen character masturbating and uttering foul language in "The Exorcist" would not be allowed.

As it is, production of those films was banned in California, which has the stiffest child labor laws and codes in the country. There, children are not allowed to be filmed nude or using foul language.

"I would not allow 'The Exorcist' to be filmed here, so they went to New York. Jody Foster and her mother even moved to Delaware to establish the necessary residency in order to film 'Taxi Driver' there," said Colleen Logan. Los Angeles administrator for the labor standards division of the California labor department.

Sponsors of federal legislation state that questionable scenes would either have to be cut or played by actors and actresses 16 years or older.

Logan, who decries the fact there are no federal laws to protect child actors and actresses from possible sex exploitation, stresses, "We are not censors. It's the use of the performing children that concerns us, not the viewers."