Figures quoted in the Daily Telegraph have revealed that some GPs are covering lists of up to 9,000 patients.
The newspaper found that more than a million patients are registered with a GP who cared for around 3,000 patients; twice the average list size of 1,600.
It reported that the Centre of Workforce Intelligence recommended earlier this year that an extra 450 GP training posts should be filled each year over the next four years.
GP leaders warned that GP shortages and increased list sizes could adversely affect patient care.
Speaking to The Telegraph, NHS Alliance chief executive Dr Michael Dixon said it was a question of whether doctors were 'able to cater as well for each patient with a list once they get much over 2,000 or 3,000'.
‘We’re not producing enough GPs as opposed to specialists. Our workforce is in the wrong place. It’s in hospitals whereas it needs to be in the community,' Dr Dixon said.
Professor Aneez Esmail, of Manchester University, told The Telegraph the problem was made worse by the retirement of Asian GPs.
Conservative MP for Totnes, Devon, and former GP Dr Sarah Wollaston told the newspaper that an increase in the number of female GPs could create problems for the profession.
‘It creates all sorts of pressures as women take time out with family commitments. There is a real risk of a shortage.’
Research by the Royal College of Physicians found that by 2013, female GPs would outnumber their male colleagues.