A fight on reality TV show Big Brother, which was broadcast live on digital TV, was too violent and not stopped soon enough, media watchdog Ofcom has ruled.
The warring parties had to be held apart during the fight
The brawl was on Channel 4 digital arm E4 in the early hours of 17 June. Ofcom upheld 55 complaints, with some viewers so distressed they also called police.
Complaints ranged from concern over the violence to the effect on housemates.
The "intensity and repetition of verbal and physical violence exceeded viewers' expectations", Ofcom said.
"Some viewers felt this was not only offensive and distressing to watch, but that it exploited certain housemates," Ofcom said.
The drunken brawl broke out when contestants Michelle and Emma were unexpectedly reintroduced to the house after spending several days in an adjacent "bedsit".
Security guards stepped in and the live TV pictures from the house were cut for an hour following a violent confrontation between Emma, Victor, Jason and Nadia.
But Ofcom criticised Channel 4 for allowing fight to go on for 20 minutes before the guards intervened.
The watchdog also criticised Channel 4's decision to continue showing viewers' text messages on screen during the brawl.
But Ofcom did not uphold 190 complaints from viewers who complained about the Channel 4 edition of Big Brother the following evening, which showed edited footage of the fight.
In its ruling, Ofcom said: "We acknowledge the concerns of the viewers of Big Brother Live on E4... who saw a potentially dangerous situation develop and who had no way of predicting the outcome of the situation.
"This was so frightening and concerning for some viewers, so much so that some called the police.
"While accepting that security men may have been positioned, the production team's eventual intervention appeared to be too late, particularly since the confrontation had turned physical."
In a statement, Channel 4 said lively competition and confrontation were "part of the appeal of a game show like Big Brother".
"Very occasionally, during live streaming of Big Brother on E4 we have to make difficult judgements about what makes acceptable viewing," the channel said.
"Although feelings were clearly running very high on 17 June, the argument primarily involved pushing and shouting.
"The producers at the Elstree studio were very confident that the situation in the house was under their control and that all the Big Brother competitors were safe."
Producers kept the fight on air until it had died down "to reassure viewers that the outcome was not as bad as they might otherwise have imagined", it added.
Ofcom did not uphold complaints from 83 viewers who were concerned about how the fight affected the well-being of the contestants and Emma's subsequent eviction.
A further 240 complaints were received by Ofcom about various other issues in Big Brother 5, none of which were upheld.
They included complaints that nudity equated to "soft porn" and a "racist term" was used to describe Victor in a viewer's text message.
Other viewers complained about Michelle and Stuart's "sex" under the table as well as offensive language and aggressive behaviour.