The first episode of ITV fantasy drama Jekyll and Hyde was broadcast too early to be suitable for young children, media watchdog Ofcom has ruled.
Ofcom found several scenes in the first episode, broadcast at 18:30 on 25 October last year, "were likely to frighten and disturb younger children".
ITV had argued it had warned viewers about the content and that most of the violence depicted was "fantastical".
But Ofcom disagreed, describing the violent scenes as "dark and menacing".
The media watchdog received more than 500 complaints from members of the public about the episode.
It noted six scenes in particular which were a cause for concern - a man being attacked in a street as the programme opened, a girl trapped under a truck with Mr Hyde leaning over her, another scene featuring a monster called The Harbinger, a fight in an alley, a nightclub fight and a family attacked in their home at night.
ITV said the street attack was "stylised and non-realistic throughout" and the truck scene was "brief and limited" and "editorially justified".
The broadcaster also argued The Harbinger scene "was not unsuitable for children", the alley fight was shot in a "stylised and non-realistic manner" and the family death scene was "suitably limited". It added the nightclub fight scene was "highly unrealistic".
But while Ofcom recognised the programme as a whole did contain elements of fantasy, "the scenes of fantasy noted above depicted relatively realistic and brutal acts of violence".
It also noted five of the six scenes highlighted were broadcast between 18:30 and 19:00.
While it took on board ITV's point the audience might have had some idea of the tone and content given the well-known novel on which the series was based, "viewers may not have expected this programme to contain violent and scary scenes... and in the first 30 minutes".
It also dismissed ITV's defence it was "unlikely that many children, particularly young children... would be preparing for bed at this time".
Ofcom also stated it "did not consider the pre-broadcast warning in this case was adequate".
The watchdog acknowledged the "programme's content was not so strong that, with the appropriate scheduling, it could not be broadcast pre-watershed".
But it "would have exceeded the expectations of viewers, and in particular parents and carers, at this time and on this channel" and ruled that ITV had breached a rule stating "children must be protected by appropriate scheduling from material that is unsuitable for them".
Another programme found in breach of Ofcom rules was the BBC's The One Show, after 11 people complained about a joke made by the comedian Jimmy Carr broadcast on 4 November.
Carr said live on air: "I tried to write the shortest joke possible, so I wrote a two-word joke, which was: 'Dwarf shortage'. Just so I could pack more jokes into the show. (Looking into the camera). If you're a dwarf and you're offended by that: Grow up!"
Towards the end of the programme, just before 20:00, presenter Matt Baker said: "Listen, just a quick word to say that if anything that... Jimmy has let slip tonight that, er - was a little bit close to the mark maybe - but we're sorry, we're sorry."
"Substantial level of offence"
The BBC said "while The One Show production team takes a particular view on the tone they would like to adhere to, and feels this joke was inappropriate in light of that, the BBC does not believe that it amounted to a breach of the code".
Ofcom rules state that: "In applying generally accepted standards broadcasters must ensure that material which may cause offence is justified by the context…
"Such material may include, but is not limited to, offensive language, violence, sex, sexual violence, humiliation, distress, violation of human dignity."
Ofcom said: "In our view, it would have been clear to the audience - and a substantial level of offence would have been likely to have been caused - by Jimmy Carr combining his initial joke (Dwarf shortage) with his follow-up statement ('If you're a dwarf and you're offended by that: Grow up!') in order to derive humour from people with the medical condition of dwarfism."
In light of the incident with Carr, the BBC said it had amended the letter guests are asked to sign prior to appearing on The One Show to include the following line: "Jokes made at the expense of minorities are likely to cause offence, so please save them for other arenas."
Meanwhile, the watchdog also decided it would not investigate viewer complaints about Channel 5's Celebrity Big Brother.
Ofcom received 418 complaints relating to comments about sexuality made by Winston McKenzie during the programme's launch show on 5 January.
In his entry video, the London Mayoral candidate said he would "cope with a homosexual in the house" by "standing against a brick wall all the time".
Ofcom said it assessed the comments but decided they did not warrant an investigation.
"We are satisfied that Channel 5 broadcast clear and appropriate warnings about the potentially offensive content," it added.