Some GPs have five times the number of patients than others, research shows.
Rural areas and London have the most GPs per population
The worst area was Greater Derby where there was one GP per 3,428 residents, the study by market intelligence specialist GMAP Consulting revealed.
Doncaster East had the second highest rate, one GP per 2,286 people, whereas the Western Isles had one family doctor for every 680 people.
But health officials cast doubt on the figures while acknowledging there was a GP shortage in some areas.
A Department of Health spokesman said there was actually less than 2,000 patients for each GP in Greater Derby and the research did not give an accurate picture of what was happening.
"There are more GPs in the NHS than at any time in its history and patients nationwide are benefiting from the fastest treatment in a decade."
Areas with lowest number of people per GP
680 - Western Isles
717 - Westminster
874 - Highlands
895 - North and West Belfast
971 - Borders
And Trish Thompson, director of operations, at Greater Derby Primary Care Trust, put the ratio at 1,916 patients per GP.
But she added: "There's a national shortage of GPs and I'm sure in Derby we are no different to the rest of the UK.
"We have been very successful recently in some campaigning to recruit new doctors into the area."
Dr Maureen Baker, honorary secretary of the Royal College of GPs, said the GMAP survey had used a "crude method" to calculate numbers.
But she admitted there was a shortage of GPs in some parts of the country.
She said the number of GPs needed to rise by 10,000 - about a quarter of the current total - "to provide the care NHS patients deserve".
GMAP managing director John Dobson defended the survey, saying it was an "accurate snapshot of provision".
Areas with highest number of people per GP
3,428 - Greater Derby
2,286 - Doncaster East
2,258 - Amber Valley
2,254 - South and East Belfast
2,064 - Crawley
The company compiled its figures by looking at GP numbers across 351 primary care areas and comparing that to population.
Rural regions had some of the best figures due to their larger catchments areas and low population densities. London also faired well.
Mr Dobson added: "The results have revealed a wide gap between the best and worst served areas through massive inconsistencies in the number of patients per GP."
And Dr Hamish Meldrum, chairman of the BMA GPs Committee, said: "We accept that there are differences in the patient GP ratio and that is why we have encouraged the government to look at ways to help incentivise recruitment of GPs to under-doctored areas.
"In the longer term we hope the new national GP contract will encourage more doctors to train to become GPs."