Television's watchdog will tomorrow slam the broadcast of explicit content in a show watched by children, as it lays out a new hardline stance against sex on screen.

The Broadcasting Standards Authority is expected to rule against TV3 for screening steamy content on Home and Away, a usually innocuous Australian soap.

The authority had turned down a previous complaint against the soap for showing two teenagers in bed, filming themselves with a video camera.

The show came under fire in Australia when it introduced a lesbian love plot. Channel Seven censored a scene showing two women kissing.

Home and Away screens at 7pm in Australia but in New Zealand it screens before the weekday news at 5.30pm.

And with new members this year, the BSA wants to signal a tougher line on sexual content and early evening programming.

The Home and Away ruling is seen as a shot across the bows of the main free-to-air broadcasters, TVNZ, TV3 and Prime.

In 2008 the BSA found against TVNZ's Shortland Street for depicting gay oral sex on primetime television. It is now expected to crack down on sex during "children's interest" programming.

BSA chief executive Dominic Sheehan confirmed that a decision would be issued tomorrow that would be "topical" and "fuel for discussion".

He said in the past two years he had noticed an increase in people approaching him with concerns about sexual content in primetime television.

TV3 spokesman Roger Beaumont refused to comment before the decision was made public.

The BSA has two new members: Chairman Peter Radich, a lawyer, and former TV journalist Leigh Pearson. They join journalist Tapu Misa and lawyer Mary Anne Shanahan.

Members of the board would not talk about the case, referring all media comment to Sheehan.

The BSA works on a complaints-based process. It can penalise broadcasters that breach standards with fines of up to $5000, take advertising time off them or, in very serious cases, take the station off the air.

Last month, the board upheld a complaint against TVNZ by Christchurch mother-of-five Melanie Riwai-Couch regarding a sex scene in Band of Brothers, which screened after the 8.30pm watershed.

TVNZ said the scene was acceptable because it didn't air until 8.40pm but the BSA disagreed.

It found the scene had "strong adult content" and screened close to the 8.30pm watershed when children could still be up. It found TVNZ had failed to adequately consider the interests of child viewers but did not hand down any penalties, to Riwai-Couch's disappointment.

Family First national director Bob McCoskrie has two complaints pending with the BSA, against a segment on porn that screened on TVNZ's Close Up, and a report about naked rugby on TV3's Nightline.

McCoskrie said there was a disturbing trend towards sexualising the news.

"You sit down and expect to get the facts of the day but instead we get full-frontal nudity and sex talk. It's a joke," he said.