Millions of patients in England wait a week or longer to be seen by their GP surgery, official NHS figures reveal.
The Royal College of General Practitioners, which analysed the data, says it expects the delays to worsen.
It says demand is growing due to a rising population, yet fewer trainee doctors are being directed to general practice to meet this need, rather than hospital medicine.
This will put more pressure on accident and emergency departments, it warns.
If people cannot see their GP promptly, some will visit the emergency department instead, says the RCGP.
According to NHS England’s latest GP Patient Survey, the proportion of patients in England who are having to wait a week or more for an appointment has risen to 15%, compared to 14% a year ago.
Based on these findings, the RCGP estimates some 26.2m patients waited a week or more to see or speak to their GP, and 46.8m waited a week or more to see of speak to a GP or nurse at their practice.
But the GP Patient Survey data, involving nearly 1m respondents, also shows 92.2% of people find making a GP appointment convenient.
The RCGP says more investment is needed in general practice, which currently receives just over 8% of the total NHS budget.
And it wants more graduates to be trained as GPs.
In 2012 – the latest year for which figures are available – there were 31,700 GPs compared to 38,200 hospital doctors.
RCGP Chair Dr Maureen Baker said: “It is vital to ensure that patients are able to access their local GP quickly and effectively – just as it is important for hospitals to have adequate numbers of qualified consultants to look after patients who are in need of acute health care.
“We need to ensure that we have enough GPs to provide patients with good access to high-quality health care in local communities across the UK.”
She warned: “If waiting times get longer, it will be more difficult for GPs to ensure that problems are caught early, and the pressure on A&E will intensify. This is bad news for patients and bad news for the whole of the NHS.”
Health Minister Dr Dan Poulter said: “The recent GP survey showed that 86% of patients rate their overall experience of their GP practice as good.