Greater Manchester Police believe they have enough evidence to bring 23 more charges, but the Director of Public Prosecutions, David Calvert-Smith, QC, has decided not to proceed, saying "enormous publicity" from the 54-year-old GP's trial would make a fair hearing impossible.

There is sufficient evidence to proceed against Harold Shipman, but I have reluctantly concluded that it would be wrong to proceed to a second, and possibly third, trial

David Calvert-Smith, Director of Public Prosecutions

A further trial would also hold up moves for a public inquiry into the case - Shipman is Britain's worst ever serial killer.

He was jailed for life in January for murdering 15 women patients by injecting them with diamorphine, commonly known as heroin.

He has also been struck off the medical register by the General Medical Council.

Police have been investigating a further 160 cases involving Shipman, who practised in Hyde, Greater Manchester.

Exceptional course

Mr Calvert-Smith said: "There is sufficient evidence to proceed against Harold Shipman, but I have reluctantly concluded that it would be wrong to proceed to a second, and possibly third, trial in respect of 23 further alleged murders. This is a quite exceptional course I have taken.

"It would be hard to find a jury in England and Wales that was not seriously affected by it," said Mr Calvert-Smith. "It is most unlikely that a judge would allow further trials to take place against that background."

He had also taken into account that the first trial had to be limited to 15 charges of murder so that the jury was not overburdened. It had lasted four months and the jury were in retirement for more than a week.

Mr Calvert-Smith said that a "considerable majority" of the relatives of alleged victims spoken to by the police accepted that a second trial could not take place.

Life in prison

"Harold Shipman has already been sentenced to life imprisonment with the recommendation that he serve the rest of his life in prison. There is nothing further the criminal law can do to increase the sentence."

He added: "The process of a second and third trial may significantly delay or hamper the progress of the public inquiry."

Mr Calvert-Smith said that consideration of other deaths of alleged victims of Harold Shipman would now be a matter for the coroner.

Jane Ashton-Hibbert: 'Families are devastated'

It was announced yesterday that the independent inquiry to be chaired by Lord Laming will be held in Manchester to allow relatives of victims access to the proceedings.

Greater Manchester Police refused to comment on the DPP's decision. It said in a statement: "Twenty-three files relating to the other deaths were passed to the prosecuting authorities some time ago.

"The decision on whether or not to prosecute on those files lies entirely with the CPS. It is force policy not to comment on decisions made by the CPS."

Jane Ashton-Hibbert, the granddaughter of one of the additional 23 alleged victims Hilda Hibbert, told the BBC the family were "devastated" by the DPP's decision.

She said: "We still want answers. Murder is murder. We realised it could not go to a public trial with a jury because it could not be a fair trial.

"But we need some recognition of the pain and suffering that we have suffered at the hands of Dr Shipman."

She said families of the 23 women would now be meeting to discuss thier next steps but no decision had been taken on the possibility of bringing private prosecutions.