LOS ANGELES, USA  (AP) — Los Angeles County voters have approved a measure requiring porn performers to wear condoms while filming sex scenes, prompting a pledge by the adult entertainment industry to sue to overturn the measure.

With 100 per cent of the county's precincts reporting, Measure B passed 56 percent to 44 per cent in Tuesday's election.

The measure requires adult film producers to apply for a permit from the county Department of Public Health to shoot sex scenes. Permit fees will finance periodic inspections of film sets to enforce compliance.

The AIDS Healthcare Foundation, which sponsored the initiative, says the measure will help safeguard the public, as well as porn workers, from sexually transmitted infections.

But the adult film industry, which is largely centred in the San Fernando Valley in suburban Los Angeles, says the requirement is unnecessary since the industry already polices itself by requiring performers to undergo monthly tests for HIV and other infections.

The industry also says porn viewers will not watch sex scenes with condoms, forcing adult film producers to relocate to where they can make movies that will sell.

On Wednesday, the Free Speech Coalition, a trade group representing the adult entertainment industry, said it plans to file a lawsuit to overturn the condom requirement on constitutional grounds.

"We believe in the calm, serious deliberations of the legal system, we will find that Measure B is in fact unconstitutional," Diane Duke, the coalition's executive director, said in a statement. "The adult film industry will not just stand by and let it destroy our business."

In a letter sent to the county Board of Supervisors, the industry also requested that it be involved in discussions as to how the county will implement the requirements. It will also explore moves to neighbouring states as soon as possible, the coalition said.

About 200 companies produce adult films in Los Angeles. A two-year health permit would cost about US$11,000, comparable to permits for tattoo and massage parlors, Weinstein said.