Speaking outside the court after being acquitted of the murder of 85-year-old George Liddell, Dr David Moor said: "The last two years leading up to the trial have been very difficult for me and my family, and the recent weeks have been devastating.

"In caring for a terminally-ill patient a doctor is entitled to give pain-relieving medication which may have the incidental effect of hastening death.

Dr David Moor: I am obviously extremely relieved

"All I tried to do in treating Mr Liddell was to relieve his agony, distress and suffering.

"This has always been my approach in treating my patients with care and compassion.

"Doctors who treat dying patients to relieve their pain and suffering walk a tightrope to achieve this."

Dr Moor was accused of murdering Mr Liddell by administering a fatal dose of the painkiller diamorphine.

The Northumberland GP admitted that he had given Mr Liddell a dose of diamorphine to relieve pain, but said he had not deliberately set out to kill him.

The BBC's Richard Wells: The police were called in after the BBC interview

He said that Mr Liddell had been in extreme pain, and the court was told that at one point the retired ambulanceman had cried out in agony and begged Dr Moor to stop his suffering.

During the trial the jury was told that in a conversation Dr Moor had admitted to helping approximately 300 patients die pain free deaths over the past 30 years.

The jury took 69 minutes to reach its verdict after an 18-day trial. When the verdict was announced the court room at Newcastle Crown Court erupted into cheers.

Dr Moor has long been a supporter of euthanasia.

In 1997 in interviews for radio, television and newspapers he openly admitted to helping many terminally ill patients who were in pain and distress to die by administering fatal doses of the painkiller diamorphine.

The BBC's Tim Smith: The courtroom erupted with cheers and applause

When asked in a BBC interview how many times he had helped patients to die, he said: "I would say many times over the 30 years I have been in practice.

"Basically you address their problems and address their needs and if they have a lot of pain, if they have a lot of suffering, and if the patient's relatives are suffering then you address that with care, compassion and consideration - I would certainly say that over the years I have helped a lot of people to die."

Dr Moor admitted in the BBC interview that he had probably broken the law.

But he said: "I am acting with care, compassion and consideration on behalf of my patients, and I have no problem with that."

Patient support

Dr Moor received widespread backing for his actions from his patients, who formed a support group, held public meetings and gathered petitions in his support.

Fiona McAndrew: We are delighted by the verdict

Support group member Fiona McAndrew said: "We are absolutely elated by this verdict, it is fantastic news.

"This case should never have been brought trial. The dignity that Dr Moor gave George Liddell in life has been taken away in death - these people should hang their heads in shame."

John Oliver, general secretary of the Voluntary Euthanasia Society, said Dr Moor was being punished for being honest.

"It was outrageous that this doctor has been dragged through the courts," he said.

But Peggy Norris, of the anti-euthanasia group Alert, said care for the terminally ill should not involve hastening a patient's death.

"This myth is being put out all the time that the doctors walk a tightrope - I've never heard such rubbish in my life," she said.

"We might as well say that the hospice people are walking a tightrope all the time."

Major implications

BBC Health Correspondent Fergus Walsh: "Many doctors have speeded up a patient's death"

It is thought the not guilty verdict returned on Dr Moor could have major implications for the practice of medicine in the UK.

Euthanasia is illegal in the UK, and the British Medical Association is officially opposed to mercy killing.

However, doctors are allowed to administer potentially lethal doses of drugs, provided the primary intention is to relieve suffering.

Many doctors say the current situation is unsatisfactory, and fear they could be prosecuted simply for putting their patients' best interests at heart. They want the law to be made more explicit.

A Department of Health spokeswoman said there were no plans to relax the legal ban on euthanasia.