Channel 4 has insisted it did not mislead the main source in its film Ian Brady: Endgames of a Psychopath, which airs on the channel tonight.
The Moors Murderer's mental health advocate Jackie Powell initially cooperated with film-makers only to withdraw her consent after a private viewing of the documentary.
Last week Powell was arrested and questioned by police after C4 publicity around the central revelation in the film – that Brady had given her sealed envelopes, one of which could reveal where 12-year-old Keith Bennett was buried by Brady in 1964.
Bennett's mother Winnie Johnson died on Saturday aged 78, unaware of the controversy around the film. Channel 4 told Press Gazette today that her family has given approval for the film to be shown.
Powell told The Sunday Times: 'I feel betrayed, I feel used, I feel abused, I feel as if I've been tricked into giving information, lied to.' She believes her arrest was the result of publicity for the film, which she has described as 'sensationalist trash".
According to The Sunday Times, she said she had been led to believe the documentary would be an ethical, sensational examination of Brady's case.
Powell told the paper she had withdrawn her consent to be included in the documentary and that scenes were recorded without her knowledge.
Channel 4 spokeswoman Marion Bentley told Press Gazette: 'At no point was she misled in any way.
'All assurances were given in good faith but because she declined to act on the letter, we felt we had to inform Winnie's family and there was compelling public interest in making this information public given: Winnie's declining health, the continued speculation of Brady's imminent death and the fact that 47 years have elapsed since Keith Bennett's murder and Brady is the only person who can identify the location of the grave.
'Both Channel 4 and the production team went to great lengths to explain our decision to Ms Powell and to show her the film – again offering her the opportunity to do the right thing and notify the police herself about the existence of the envelope and hand its content over to the authorities.
'We believe this documentary presents further important evidence of Brady's ongoing attempts to manipulate and psychologically torture his victims' families.
'Given the compelling public interest in the information she disclosed in an interview with the director, we feel, after careful consideration, that we have a duty to make this public – and we feel we have to show the interviews with Jackie to provide the context in which the letters came to light.
'There is nothing in the film that is reported speech from Jackie. Everything used in the film is what she told us on camera. We do not speculate at all about anything off camera."
Ian Brady: Endgames of a Psychopath airs on Channel 4 tonight at 9pm.