The Director of Public Prosecutions will today publish his final guidance on the circumstances in which someone may be charged for helping another person to die.

Keir Starmer QC was asked to draw up the guidance after multiple sclerosis sufferer Debbie Purdy won her legal battle for clarification on the law in the House of Lords last year. She asked to know if her husband would be charged if he helped her to end her life.

Writing in The Times today, Mr Starmer said a distinction needed to be made between people who helped a loved one to die and those who took another life.

He wrote: "Assisted suicide involves assisting the victim to take his or her own life. Someone who takes the life of another undertakes a very different act and may well be liable to a charge of murder or manslaughter. That distinction is an important one that we all need to understand.

"Each case is unique, each case has to be considered on its own facts and merits; and prosecutors have to make professional judgments about difficult and sensitive issues. The assisted suicide policy will help them in that task."

The eight pages of guidelines will be released this morning together with a 45-page summary of some 5,000 responses to the interim policy published last September, which stated that someone who helped another person to die on compassionate grounds was unlikely to face prosecution.

The guidance will not change the law, which makes assisted suicide a criminal offence punishable by up to 14 years in prison. It has, however, raised concerns that the seriously ill will feel under pressure to end their own lives.

Writing in The Daily Telegraph yesterday, Prime Minister Gordon Brown said developments in palliative care in the last few decades had weakened the case for legalising assisted suicide.

“The law – together with the values and standards of our caring professions – supports good care, including palliative care for the most difficult of conditions, and also protects the most vulnerable in our society,” he said.

“For let us be clear: death as an option and an entitlement, via whatever bureaucratic processes a change in the law might devise, would fundamentally change the way we think about mortality.

“The risk of pressures – however subtle – on the frail and the vulnerable, who may feel their existences burdensome to others, cannot ever be entirely excluded. And the inevitable erosion of trust in the caring professions – if they were in a position to end life – would be to lose something very precious.

Church leaders including the Archbishop of Canterbury Dr Rowan Williams and the Archbishop of Westminster Vincent Nichols have spoken out against any change to the law in recent weeks.

Dr Williams warned it would be a “moral mistake” to legalise assisted suicide. He said a change to the law would “cross a moral boundary” and leave the vulnerable in society feeling manipulated, harassed or demoralised.