The NHS is investigating claims by an undercover reporter that suicidal people calling the NHS 111 helpline are being left on hold until they hang up and that some staff are asleep on duty.
The Sun placed a reporter at the NHS 111 call centre at St Charles Hospital in Ladbroke Grove, west London, which provides 24-hour support for callers from 11 boroughs in north, west and central London.
I was asking her stuff like, 'do you not really want to talk', she was like, 'no'... I put her on mute
The newspaper said it found call handlers asleep at their desks or describing themselves as "busy" on the internal computer system to avoid new calls and new patients.
Technical glitches reportedly ended with one handler hanging up on at least three patients, including one with heart palpitations.
Workers were told to tell callers they were experiencing technical failures when they may have been struggling to work the system, according to The Sun.
The newspaper reported an alleged conversation with one of the handlers about how she dealt with a suicidal patient. It said the handler told the undercover reporter "she was crying and I was asking her stuff like, 'do you not really want to talk', she was like, 'no'... I put her on mute".
The report also claimed that managers changed the undercover reporter's time sheets to show he had done more training hours than he had.
A Department of Health spokesman said: "The NHS is now urgently investigating and if any wrongdoing whatsoever is found, including criminal actions, we will want to see the police and relevant NHS regulators alerted as necessary."
He described the claims as "clearly completely unacceptable" if found to be true.
Simon Douglass, medical director of the London Central and West Unscheduled Care Collaborative, which runs the centre, said: "I would like to reassure patients and the communities that patient safety is, and always will be, our highest priority.
"We take any allegations extremely seriously and have launched an urgent investigation. The matters leading to the allegations appear to have arisen earlier this year when the undercover reporter participated in training.
"All issues relating to staff conduct are extremely important to us, particularly in relation to patient safety. We strictly enforce our policies for managing staff conduct at all times including whenever we receive reports of inappropriate conduct or behaviour.
"We are working closely with the NHS clinical commissioning groups to ensure that any concerns are thoroughly investigated and we have appointed a senior investigating officer to oversee this process.
"The Sun did not share their evidence prior to publication and we will be asking them to disclose this to us to assist our investigation.
"As an NHS service provider we are committed to delivering high-quality services."