The country's two main broadcasters have been told off for airing sexual scenes - one during children's viewing times - breaching broadcasting standards.

Both TVNZ and TV3 said last night they are considering appealing against the decisions after the Broadcasting Standards Authority upheld complaints against them.

TVNZ had a complaint upheld for showing a man performing oral sex on a woman in the controversial comedy-drama Hung, while TV3 was found to have breached three broadcasting standards for a "raunchy" scene in the early-evening soap Home and Away.

Despite having an "adults-only" rating, a verbal and written warning about the content and its 10.10pm screening time, the authority described the scene in Hung as "soft porn" that went "well beyond the level of sexual material that viewers would expect to see on free-to-air television".

"The scene complained about was prolonged, explicit and gratuitous, leaving nothing to the imagination and designed solely for the purpose of shocking and titillating the audience," the decision said.

"The programme's AO classification and the use of a written and verbal warning were not sufficient to prevent the broadcast breaching standards of good taste and decency."

The complaint follows earlier concerns about a billboard promoting Hung in Auckland's Victoria St which featured a three-dimensional bulge covered in white material.

The programme is about a man with a large penis who starts working as a male prostitute.

Complaints that the billboard was offensive to young children and their families were not upheld in May because children would not be able to understand the message and the advertisement was in a location primarily viewed by adults.

Meanwhile, TV3 has placed the clip of its "sexually charged" scene on its website for viewers to decide whether the interlude is offensive.

The scene shows two adult characters, Liam and Martha, kissing before she straddles him on the kitchen table. It was found to have breached three standards relating to responsible programming, children's interests and good taste and decency: "This scene would have been alarming and distressing to young children when not subject to guidance" and "went well beyond the level of sexual activity that should be included in a G-rated programme," the authority said.

TV3's lawyer, Clare Bradley, said the broadcaster was surprised the complaint was upheld and had not meant to give any viewers a shock.

"Our appraisers looked at it, the standards committee looked at it, we considered it in-house pretty carefully and formed a view that it was fine."

It is the first time that a complaint about sexual content in Home and Away has been upheld.

Bob McCoskrie, national director of lobby group Family First NZ, welcomed the BSA decisions.

"Finally, the authority has put the welfare and protection of families before the rights of broadcasters to offend children and families with sexual and offensive content ... perhaps, finally, they have woken up.

"Our research has shown that the 5pm-8.30pm viewing slots, ironically named 'family viewing' times, are anything but family-friendly.

"They are saturated with foul language and sexual images, themes and innuendo.

"We hope this sets an important precedent, and that families can grab back their family viewing times."

Both TVNZ and TV3 must publish the BSA decision as penalty for the breaches and have 20 days to appeal.