The son of one of Harold Shipman's victims has described him as a "good doctor" and feels the killing of his father was an act of euthanasia.

Jack Shelmerdine said following the death of his father, also called Jack, his family believed his death was due to patient care at the hospital where he stayed, rather than the hands of his GP.

He added that he stills maintains the "twisted logic" that Shipman killed his father through euthanasia, rather than think of it as murder.

Shelmerdine made the remarks in a two-part Channel 5 documentary marking 10 years since Shipman's suicide.

The GP was sentenced to life in 2000 for killing 15 patients in Manchester and was later found to have killed an estimated 250 people over a 23-year period, making him one of the most prolific serial killers of all time.

He was found hanged in his cell at Wakefield Prison in West Yorkshire on 13 January 2004.

Shelmerdine said: ''It's an odd situation that he killed my father and that I still think he was a good doctor. The two don't seem reconcilable. I can't explain the attitude I have. I mean, logic says you should hate the man but, I don't know.''

Shelmerdine also recalls being present when Shipman administered the lethal injection to his father.

He added: "I was concerned that my father was still unconscious, still asleep as we were thinking, and I rang Dr Shipman and I remember his words were, 'Oh, he might well make it'. But those words, 'he might make it' seemed odd to me.

"And I just wondered whether questions ought to be asked. I wasn't thinking in terms of Dr Shipman having done anything. We were more inclined to think that the hospital had done something wrong rather than Shipman.

"It is murder, but I would like to think of it as euthanasia. Twisted logic. That's life."

In the first programme, Harold Shipman: Driven To Kill, a former colleague from his early years also described Shipman as a ''brilliant doctor'' who the patients "couldn't ever say a bad thing about".

Margaret Sivorn, who worked with Shipman at Pontefract General Infirmary, added: ''They felt calm and comfortable with him and knew that he was looking after them properly. He was always professional, always, and you always felt at ease with him.

"He'd have a smile with them, a little joke with them, but professional to his fingertips.''

Harold Shipman: Driven To Kill will be shown on Channel 5 at 9.00pm on 17 April. A second programme, Harold Shipman: Catching Dr Death, will be screened the following week.