Practices are facing growing pressure from patients who cannot get hospital outpatient appointments, experts have warned.

More than two million patients have been unable to get outpatient appointments this year following GP referrals – in another hidden waiting list, it has been revealed. The number of so-called ‘appointment slot issues’ has increased by half in the last two years, the Sunday Telegraph revealed. It found 2.3 million people were not given appointments between January and June. Hospitals are meant to retain details of these patients and find them appointment times – but GP leaders say they often end up returning to seek help from their practice.

The Royal College of GPs said patients were facing an “unacceptable” situation because NHS rules allow patients to be removed from this waiting list if no appointment is found within six months.

NHS Digital, which collects the figures, warned: “Appointment slot issues compound waits by creating a backlog of patients whose waiting time has already started, creates a significant amount of avoidable administrative work and can cause patient safety issues.”

NHS England disputes that patients with appointment slot issues can be removed from waiting lists. GPs say that failing to give patients an appointment loads more pressure onto practices – as patients will return to the GP to find out what has happened.

RCGP vice-chair Dr Gary Howsam said: “GPs work very hard to refer patients appropriately, and timely treatment can make all the difference – so it is unacceptable if patients find themselves back to square one because of delays that are no fault of their own. Backlogs also place additional pressures on general practice at a time when our service is already stretched beyond endurance.”

The Patient Safety Learning charity recently reported hearing from GPs who say they cannot get referrals accepted.

One doctor, from the North East, said: “There is an ever-creeping transfer of management of complex conditions from secondary to primary care, without adequate training or resources to manage this safely. Locally, we have just lost our general geriatric clinic, where we would refer older patients with several serious conditions on numerous medications. As GPs, we do not have the capacity, resources or expertise to do a full geriatric assessment, and yet that is what we have been left to attempt.”

Chief executive Helen Hughes said: “We believe that NHS England needs to urgently investigate, quantify the scale of the problem and take action if we are to prevent these capacity and system issues resulting in avoidable harm for patients.”