Dame Janet Smith is heading the inquiry

The inquiry at Manchester Town Hall heard on Monday, Mr Pollard had "relied entirely on the probity of the police to look at matters properly".

Dame Janet said his apparent lack of interest in the investigation was "strange".

Mr Pollard told the hearing he was approached by Dr Linda Reynolds, who worked at the Brooke Surgery near Shipman's practice.

She told him she was concerned at the number of times Shipman was present at the death of his patients.

He said he reported the allegations to police and then had no contact with the detective carrying out inquiries until the four-week investigation was closed.

When told there was nothing suspicious about Shipman, the coroner accepted it without question.

'Deeply puzzled'

Dame Janet interrupted proceedings to express her surprise that Mr Pollard did not press the detective further as to what had led him to bring his inquiries to a close.

She told Mr Pollard: "I would just have thought you would have been deeply puzzled and curious and that your curiosity would have been even greater as a coroner than it would have been for an ordinary person."

But Mr Pollard said that while interested in the allegations, he was always aware that Shipman may have been simply an "old fashioned doctor calling in on his patients unannounced".

Dame Janet later pushed the coroner, saying: "I must confess I find it strange you did not ask for more explanation."

Mr Pollard answered: "It comes back every time to the two explanations that were put forward at the very outset."

Either Shipman was a serial killer, or simply a very good, "old fashioned" GP, he said.

Insufficient evidence

Last week, Dr Reynolds' widower, Nigel, told the inquiry how he and his wife - who died in early 2000 - talked incessantly about Shipman during that initial investigation.

Dame Janet added: "One of the things [Mr Reynolds] said was that he and his wife talked around this issue up hill and down dale. That I can understand."

As a family doctor in Hyde, Greater Manchester, Shipman murdered 15 of his women patients and is now serving a life sentence in prison.

The inquiry into the convicted serial killer is investigating why the preliminary police inquiry found insufficient evidence to proceed against the GP.

The inquiry began in June 2001 and may last up to two years.