The launch of NHS 111, a new telephone helpline in the UK that was due to debut on 1 April, has been delayed because of technical problems during its pilot phase.

NHS England said the helpline was introduced in one area – the north of Tyne & Tees – on schedule, meaning 23 areas of England now have it in use. But the helpline is still not running in another 23 areas, or is only partially deployed.

The 111 number will not be operational nationwide until June, NHS England told the Guardian.

The NHS 111 service is designed to direct callers with non-emergency conditions to the right part of the NHS and has been trialled in some parts of the country ahead of a wider deployment.

The British Medical Association (BMA), the body that represents doctors in the UK, had called for a delay in a letter to Sir David Nicholson, the chief executive of NHS.

The BMA voiced concerns about the technical problems that are being experienced with the system. “There have been widespread reports of patients being unable to get through to an operator or waiting hours before getting a call back with the health information they have requested,” said Laurence Buckman (pictured), the organisation’s GPs committee chair.

Doctors have also complained about confusion among the public about when they should use the 111 service.

The NHS 111 is due to replace NHS Direct and GP out-of-hours numbers across most of England.

Pilot schemes have demonstrated the helpline’s shortcomings, including a system crashing in Greater Manchester because it could not cope with call volume.