BBC1 drama Red Rock breached broadcasting guidelines when it aired a violent scene in which a female police officer was attacked by three men, the TV watchdog has ruled.
The story was played out in the Irish police drama, before the watershed, in the early afternoon, in July.
Ofcom said that the violence was not "appropriately limited and scheduled before the watershed".
An Ofcom spokesman said: "This drama broke broadcasting rules because it aired a violent scene before the watershed.
"We found the violence was heightened by various factors such as the tone, music and duration of the scene, and lacked any appropriate warning."
Meanwhile, Ofcom has decided not to investigate an episode of Emmerdale after it received around 500 complaints that a storyline featuring the attempted theft of a dog could spark copycat behaviour.
The scene saw characters Charity Dingle (Emma Atkins) and Ross Barton (Michael Parr) plot to steal a dog and ransom it back to its owner.
The charity Dog Theft Action complained about the storyline.
But an Ofcom spokesman said: "We found that the scenes were not likely to condone or encourage people to attempt dog theft, taking into account the dramatic context and that the characters involved were clearly not role models.
"It was clear to viewers they were behaving in a morally questionable manner, and the attempt to capture a dog failed."