The NHS was forced to find an "appropriate" place for a vulnerable teenager who was being held in a custody cell because there were "no beds available in the UK" after an angry intervention from a senior police officer.
Paul Netherton, Assistant Chief Constable of Devon and Cornwall Police, lashed out on Twitter and appeared on television about the "unacceptable" scenario the 16-year-old girl found herself in.
NHS England said the girl will be moved from police custody to a "place appropriate for her care" - but the situation has been described as "appalling" and is said to be "becoming worryingly common".
Mr Netherton tweeted: "We have a 16yr old girl suffering from mental health issues held in police custody. There are no beds available in the uk! #unacceptable" (sic)
He added: "The 16yr old was detained on Thursday night, sectioned Friday lunchtime and still no place of safety available. This can't be right! 1/2
"Custody on a Fri & Sat night is no place for a child suffering mental health issues. Nurses being sourced to look after her in custody !?!"
A spokesman for NHS England said a "local place" for the girl has been found.
"She will be moved this evening," he said.
He added that she would be moved to a "place appropriate for her care".
In a statement, NHS England added: "A local place of care has been identified for a 16-year-old girl who was being held by the police in Devon.
"After details were provided to NHS England about the girl and her condition a place was found locally within a few hours. We are grateful for the help of the NHS in the area in identifying the place.
"It is worth noting that mental health crisis services have been expanding so that the number of people ending up in police cells is in fact down - but clearly more needs to be done."
Mr Netherton told Sky News that police would not put a criminal in custody for this long and said they certainly do not want to put someone suffering from mental health issues in a custody block for this length of time.
He said the girl was detained on Thursday night while she was at Torbay Hospital because she caused a breach of the peace.
When she got to custody she was detained under mental health powers, and the following day she was assessed by doctors who found she needed to be detained under section 3 of the Mental Health Act.
''The problem is, they had nowhere to take her, so she now still remains in our custody centre, and obviously we're very concerned about that," he said.
Mr Netherton said the force has been told there were ''no beds available anywhere in the United Kingdom''.
He said: ''We do have a problem in that we ... this last year, in Devon and Cornwall alone, had 750 people with mental health issues being detained in police stations.
''Now obviously we try and then move them on to appropriate accommodation. What concerns us in this case, and it's certainly a problem across the country, talking to my colleagues, is the fact that it involves children.
''And I do not think there's sufficient provision for children who suffer mental health issues and need to be detained in an emergency situation like this.''
Asked if he thought his position could be at risk for speaking out on Twitter about the scenario, he said: ''I don't think my position is at risk. I think we're just stating the facts.
''I think that is my job. I'm a senior police officer. I have a child who is in my care ... I have a duty of care over all the prisoners who come into the custody blocks within Devon and Cornwall, and therefore I think I need to flag it up and do something about it when we are frustrated.''
Luciana Berger, Labour's shadow health minister, said: ''This sad situation is becoming worryingly common. People shouldn't face the indignity of being kept in police cells when they are at their most vulnerable.
''The Government promised parity for mental health services, yet we're going backwards. In recent years, they have suffered more than other NHS services and are falling deeper and deeper into crisis. The NHS has lost 1,500 specialist beds and thousands of mental health nurses.
''This is an appalling reflection of the crisis in mental health services and the Government must get to grips with it.''
Dr Peter Carter, chief executive and general secretary of the Royal College of Nursing, said: ''It's appalling that any patient should be taken into police custody due to a lack of mental health beds - it's particularly unacceptable that it should happen to a 16-year-old.
''The severe pressures on mental health services are leading to shocking situations across the country.
''The last four years have seen a drop of more than 3,300 mental health nursing posts and a loss of 1,500 available beds despite a 30% rise in patients requiring mental health care.
''These cutbacks are having a devastating impact on those who desperately need care and support.
''It's a terrible indictment of this country's inadequate mental health provision.''
Mark Winstanley, CEO of Rethink Mental Illness, said: "This is a very troubling situation, but unfortunately it is far from an isolated incident.
"Each year thousands of people with serious mental health problems are being held in police cells, including many children and teenagers, because the right services either don't exist in their community or are completely overstretched."
He said if someone is going through a mental health crisis, they should be brought to a "health-based 'place of safety'".
He added: "Being held in a police cell can be extremely distressing, and should only ever happen as an absolute last resort.
"But many people are being turned away from 'places of safety', because of staff shortages or lack of spaces. In some parts of the country, there are no health-based places of safety full-stop."
Mr Netherton tweeted tonight: "Just heard that a place of care has been found for our 16yr old. Good result."
Paul Farmer, chief executive of Mind, the mental health charity, said: "This is a terrible and shameful situation. Being in mental health crisis can be terrifying and life-threatening, and people need urgent care from mental health services.
"A police cell is a completely inappropriate place to put someone who is so unwell and everyone agrees that children with mental health problems should never be put in a police cell.
"This whole episode shows how thinly spread NHS mental health services are."
Lucie Russell, director of campaigns at YoungMinds, said: "It is both shocking and totally inappropriate that a 16-year-old child has to spend two days in a police cell as she goes through a serious mental health crisis.
"It should not be the responsibility of the police to be caring for her, they are not mental health professionals nor should they be expected to be.
"This girl will look back on the crisis she experienced and remember living through it in police custody."
She said more action is needed on the ground, adding: "We need mental health services that intervene early and that care for and support our young people if their distress and pain reaches crisis point."