An explicit trailer that used two semi-naked women to advertise Channel 4's digital channel More4 broke TV rules, media watchdog Ofcom has said.
Viewers would not have expected to see such racy scenes outside the context of a normal programme and there was no warning, the regulator said.
The trailer, which played on the words "adult entertainment" to promote More4, was shown on E4 at 0010 last September.
It showed two women embracing on a bed until one lent on a remote control.
The pair began watching a More4 news report and were joined by a film crew, who it transpired had been filming them.
A viewer complained that the advert contained offensive and demeaning content and there was no prior information giving them the option to switch off.
Channel 4 argued that the trailer's provocative but humorous approach was not out of context with the material frequently seen in programmes on E4 at that time.
But Ofcom said comedy drama Six Feet Under, which preceded the trailer, did not frequently contain such graphic material and so its audience would not necessarily have expected it.
"Viewers of the channel at this time would not necessarily expect, or accept, such sexually strong material during a trailer," Ofcom said.