Retired GP Dr Michael Irwin, from Cranleigh, in Surrey, could face a jail sentence of up to 14 years for his involvement.

He admitted to conspiring to help fellow activist Patrick Kneen kill himself on the Isle of Man, after he was arrested at his home on Friday.

He was taken to Guildford Police Station before being flown to the Isle of Man for questioning.

The extent of that conspiracy was literally a few days, because it was totally impossible for him to take his own life Dr Michael Irwin

Dr Irwin resigned as chairman of the Voluntary Euthanasia Society on Saturday after returning to the UK on police bail.

He admitted on Sunday he had flown to the Isle of Man two months ago equipped with enough sleeping pills to enable Mr Kneen to commit suicide.

But the plan was abandoned when it became apparent Mr Kneen, who had prostate cancer, was so ill he would not have been able to take the pills without help.

That would have opened up the possibility of a murder charge, Dr Irwin said.

Legal battle

Mr Kneen, who died soon afterwards without assistance, had started a campaign to change euthanasia laws on the island.

His wife Pat and Dr Irwin could now face a landmark legal battle.

Dr Irwin said: "There's no point in hiding what happened, because in a strictly legal sense we did conspire to help Patrick to commit suicide because that's what he said he wanted to do and knew he was dying and only had a few weeks.

"But the extent of that conspiracy was literally a few days because it was totally impossible for him to take his own life."

He said he had resigned because it was "embarrassing" to the society to have a chairman who had broken the law.