A TV presenter's on-air confession that he killed his ailing lover is to be investigated by Nottinghamshire Police.
Ray Gosling, 70, told the BBC's Inside Out programme he had smothered the unnamed man who was dying of Aids.
Pressure group Care Not Killing said it was "bizarre" the BBC had not told police of the admission when it was filmed in December.
The BBC said it was under no obligation to report to police ahead of broadcast but would co-operate with the inquiry.
During a documentary on death and dying the Nottingham filmmaker said he had made a pact with his lover to act if his suffering increased.
In the BBC East Midlands programme, broadcast on Monday, he told how he smothered the man with a pillow while he was in hospital after doctors told him that there was nothing further that could be done for him.
Mr Gosling did not name either his lover or the hospital.
Dr Peter Saunders, from Care Not Killing, said Mr Gosling's account sounded like a case "not of assisted suicide but of intentional killing or murder".
He said: "It's rather bizarre this was filmed more than two months ago and the BBC has been sitting on it and hasn't informed the police and the case hasn't been investigated.
"At the moment all we have is Ray's word there was a pact and it wasn't clear from his description whether his lover even wanted to be killed or asked to be.
"It's not up to us as the viewing public, on the basis of one very brief selective testimony, to draw conclusions on what might be a very complex case.
"That's why it's so important all these cases be fully investigated so the true facts can come out."
Following the broadcast, police confirmed they had begun an inquiry.
A spokesman said: "We were not aware of Mr Gosling's comments until the BBC Inside Out programme was shown.
"We are now liaising with the BBC and will investigate the matter."
A BBC spokesman said the organisation will co-operate fully with the investigation.
They said Mr Gosling's "secret" was not known before he was commissioned to make the report on death and dying, adding: "The first the BBC knew of this incident was during filming for the programme that was broadcast on 15 Feb 2010.
"The BBC is under no legal obligation to refer the matter to the police in these circumstances."
In the film Mr Gosling describes smothering his lover.
He said: "I said to the doctor: 'Leave me just for a bit,' and he went away.
"I picked up the pillow and smothered him until he was dead.
"The doctor came back and I said: 'He's gone.' Nothing more was ever said.
"When you love someone, it is difficult to see them suffer."
Mr Gosling said he was aware of the possible consequences and had no regrets.
He said: "It's a terrible situation. I loved him to bits.
"We had a pact - he said if the pain gets bad and if nothing can be done, don't let him linger on.
"I don't think it's a crime.
"If he was looking down on me now he would be proud."
Sarah Wootton, chief executive of Dignity in Dying, said: "This case yet again demonstrates that this is a real and present problem, which can affect us all.
"Crucially, Ray Gosling's loved one was terminally ill and clearly asked for help to die when he was suffering unbearably at the end of his life.
"This illustrates a need for formal assisted dying legislation to help those who want choice at the end of life, as well as protect people who may be vulnerable to coercion."
The Right Reverend Tim Stevens, Bishop of Leicester, said the Church of England was against euthanasia, as it saw a need to protect the vulnerable.
He said: "The moral case is based on the fact for the Christian, all human lives are of equal value under God, regardless of whether people are sick, fragile or healthy.
"To say that it's vital to reduce the pain and distress of the terminally sick is one thing, on the other hand to say that we legitimise the premature ending of human life by direct medical intervention is another thing."
Assisted suicide remains a criminal offence, but interim guidelines issued in September by the director of public prosecutions set out the factors which weigh in favour of and against prosecution in different cases in England and Wales.
• The interview with Ray Gosling was broadcast on BBC One's Inside Out East Midlands programme on Monday evening.
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