A Labour MP has written to media watchdog Ofcom raising concerns that ITV breached broadcast rules with controversial drama The Secret.
Louise Haigh, who represents Sheffield Heeley, said the broadcaster's handling of the show was "unacceptable" and "deeply troubling" after family members of victims depicted in the crime drama complained they had not been given a chance to watch it before airing.
In a statement to the Belfast Telegraph, the MP said ITV had acted insensitively.
"The revelation that one of the families involved weren't asked if they would like to view the series prior to broadcast is deeply troubling," she added.
"ITV have a duty under the Broadcasting Code to minimise distress. The very least they should do under that obligation is allow the families to view the programme before it airs so they can make sense of it and prepare for the distress to come once it becomes national news.
"It is completely unacceptable and insensitive that ITV did not offer all of the families that option and raises serious questions about their handling of this highly sensitive drama.
"Of course, it raises serious doubts about whether they did indeed comply with the Broadcasting Code."
The Secret portrays the double murder of Trevor Buchanan and Lesley Howell in 1991, who were killed in Castlerock by their spouses Hazel Buchanan and Colin Howell, who were having an affair.
On Friday, David Stewart, who later married Hazel Buchanan, complained that the late Trevor Buchanan's children were not given a chance to watch The Secret before its air date.
The penultimate episode of the drama, which was broadcast on Friday night, shocked many viewers with graphic sex scenes involving the two murderers.
Stuart Buchanan, the nephew of Trevor Buchanan, took to twitter on Saturday to vent his frustration at the drama.
"True means accurate, exact and without variation," he wrote. "Does The Secret meet this definition? If not, is it really true?
"An approximate truth will always be partial, distorted and incomplete. Good enough truth is not good enough."
Last week, Louise Haigh raised the issue with Prime Minister David Cameron after other family members of the victims said they felt exploited by the programme. The MP had been contacted by Lauren Bradford the daughter of Colin Howell, who complained she had been re-traumatised.
In an article for the Guardian she wrote: "Behind the high viewing figures, whether for fiction or the coverage of real crimes, there are people living with murder bereavement on a daily basis. An intrusive media experience can often compound this original trauma. If deemed 'a good enough story', private grief then becomes public property."
In a statement ITV said: "The producers notified members of both the Howell and Buchanan families at an early stage of development of the drama. They provided information to both Howell and Buchanan family members who wished to be kept informed of the drama, and respected the wishes of those who did not want any involvement with the drama.
"The drama was provided to those members of the families who wanted to be kept informed and requested an advance viewing. We have never suggested that any member of either family approved or authorised the drama."