A Daily Telegraph investigation has discovered large variations in the coverage offered by out of hours doctors.

In Barnet and Enfield, 650,000 people were covered by only one doctor overnight last weekend, but the same number of patients in Shropshire and the surrounding area had eight doctors on duty.

Another  report identifies “gaping holes” in out-of-hours services and warns there could be a repeat of the errors that have contributed to the death of several patients.

Last week it was reported Suffolk has only two GPs on call on some nights to cover a population of more than 600000, and last weekend the county had three GPs available overnight.

This week a coroner is expected to complete the inquest into the death of David Gray, a 70-year-old from Mania, Cambridgeshire. Mr Gray died in February 2008 after being given a massive overdose of diamorphine by Daniel Ubani, a locum doctor from Germany who had flown in for his first out-of-hours shift.

The case has raised fresh questions about the out of hours service, from which GPs were allowed to opt out as part of the 2004 contract changes and responsibility passed to local NHS organisations.

The Daily Telegraph asked all 152 primary care trusts in England and their out-of-hours provider how many were GPs on overnight duty this weekend. Eighty-two responded, and the findings were:

• Fifteen trusts that responded left a lone doctor responsible for responding to late-night emergencies.
• Two GPs were covering 530,000 people in Sheffield.
• Three GPs were covering 991,464 people in Derby County and Derby City primary care trusts.
• Cumbria Health on Call had seven GPs covering 500,000 people – one doctor for every 71,000 patients.
• Four GPs covering 1.4m people overnight in East and North Hertfordshire PCT, West Hertfordshire PCT.
• On average across England there was one GP on call for every 154,000 people between midnight and 8am this weekend.

There were also wide variations.  Four GPs are on duty overnight for the 1.4 million people living in east, west and north Hertfordshire, but there are 11 doctors available to the same number of people living in east, north and south Birmingham and south Staffordshire.

Five GPs take care of overnight calls for service from the 708,000 people living in Dorset, Bournmouth and Poole, while only three doctors provide the same service to 780,000 in parts of Hampshire and Southampton.

Norman Lamb, Liberal Democrat health spokesman, said:

“What the Daily Telegraph has uncovered is utterly shocking.  The disparity between one area and another is hard, if not impossible, to explain or justify.

“We do not need vast numbers of doctors on call on any particular night but we do need more than what has been uncovered here.”

Mr Lamb said attendances at Accident and Emergency have risen since the new contract came into force.

Katherine Murphy, director of the Patients’ Association, said:

“It is such a vital service because it can be very frightening for somebody to get ill in the night, knowing that there’s nobody at their doctor’s surgery.

“We know from our helpline that this is a national problem. The situation is appalling and it needs to be resolved. I think these figures are absolutely scandalous.”

The Primary Care Foundation, a health consultancy service which has been commissioned by the Department of Health to audit out of hours services, found that there are “gaping holes” in services and warned that serious incidents could be repeated.