Monitor has launched a review into how easy it is for patients to access general practitioner services.
The regulator will investigate whether GP services “operate in the best interests of patients”, a spokesman said.
GP leaders recently said that family doctors were under so much pressure that they may be unable to deliver safe care for patients.
Clare Gerada, chairwoman of the Royal College of General Practitioners, said that some see as many as 60 patients a day and are struggling to cope with ballooning workloads.
Monitor has launched the examination of GP services in England and it is calling on patients, GPs and other health officials to come forward and share their experiences.
Its chief executive David Bennett said: “For many patients, GPs are the first port of call when they access NHS services and general practice has a significant impact on the wider heath sector.
“People want a good service from their GPs, they want to be able to see their regular doctor at times that suit them and they want to be able to make informed choices about their health care.
“This call for evidence is an opportunity for Monitor to learn about any barriers preventing general practitioners from delivering what is best for patients.”
The Royal College also warned that patients could lose up to 2,400 GPs following the chancellor’s decision in the comprehensive spending review that £2bn of health service funding will be put in a pooled fund for joint spending with local authorities in 2015-16, in order to integrate health and social care.
The college fears that the CSR could lead to a cut in funding for general practice and a substantial reduction in the number of GPs. Across England the funding lost would be the equivalent of the sum paid for 2,390 salaried GPs, it said.
Dr Gerada said: “When general practice starts to buckle, the entire health service comes under increasing strain and any substantial cut in the number of GPs - at a time when we are crying out for more - will have a devastating impact on our patients.”
She added: “While most people breathed a huge sigh of relief on Wednesday when the chancellor announced that the NHS budget would continue to be protected, our analysis shows that, in reality, the budget for general practice in 2015-16 could suffer from savage cuts.
“At a time when we are already struggling to cope with the demands of an ageing population and a patient client group that has increasingly complex health issues, it is ludicrous that the chancellor has put in place a programme that risks taking millions of pounds out of general practice. Right now, we need 10,000 more GPs, not 2,400 fewer.”
A Department of Health spokeswoman said: “This isn’t a loss of money from the NHS to social care - we are creating a joint fund that will benefit both.
“Spending money on social care not only provides a better service for individuals, it also eases pressure on the NHS.
“If we are to improve the care of the most vulnerable in society we have to invest in services that can help keep them out of hospital when they don’t need to be there.
“GPs will play a crucial role in this, helping to commission services with local authorities for their local population.”