TV watchdog Ofcom has warned broadcasters about airing violence before the watershed and announced that it will commission research into the issue as Channel 4 soap Hollyoaks was found to have breached programme rules.
The regulator will look at viewers' attitudes towards on-screen violence in everything from documentaries to drama, and examine whether the amount and nature of violence in soaps has changed over the last decade.
It will look specifically at shows scheduled before and immediately after the 9pm watershed.
Its announcement came as it issued a statement to "remind television broadcasters of the need to ensure that all material broadcast pre-watershed which features violent scenes is appropriately limited".
"Broadcasters should consider whether individual acts of violence within a programme are suitable, as well as where the overall tone is malevolent, menacing and threatening, that this also remains suitably limited," it said.
Hollyoaks breached broadcasting rules in an episode, screened at 6.30pm in March, in which a main character was killed by a speeding train.
The scene marked the culmination of a long-running revenge storyline involving a former undercover policeman, Walker, and ex-drug dealer Brendan.
It ended with Walker screaming as he fell backwards on to the railway track and into the path of a train before the camera cut away to show the train passing at high speed. There were no images of Walker being hit by the train but the fight in the build-up included several blows to the face and stomach, Brendan's head being pushed through railings, Walker with bloody lips and blood running from his nose, while viewers heard the groans as they inflicted blows.
Channel 4 said that the storyline had run for around a year and that viewers were notified that a dramatic episode would be broadcast. It said that the fight scene only lasted around a minute, was at the end of the episode and carefully edited.
Ofcom said that it accepted that violence was "a part of life and integral to many dramas, including those broadcast pre-watershed." But it said that the pre-programme information was too vague and would "not have prepared the significant number of younger viewers in the audience, or their parents, adequately for the violent, intense and shocking scenes which followed".