Police are being forced to hold a 16-year-old girl with mental health problems in custody as there are no available NHS beds, according to a senior officer.
Devon and Cornwall Police assistant chief constable Paul Netherton described the "unacceptable" situation involving a teenager who was detained on 27 November and sectioned the following day.
In a series of tweets, Netherton described how the girl should be "in a place of safety" but has been told there is no space for her at any hospital.
He said: "We have a 16yr old girl suffering from mental health issues held in police custody. There are no beds available in the UK.
"The 16yr old was detained on Thursday night, sectioned Friday lunchtime and still no place of safety available. This can't be right.
"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."
Other senior police officers reported similar failings on Twitter in replies to Netherton's original post.
Niven Rennie, the president of the Association of Scottish Police Superintendents, said it showed police was being treated as the "service of last resort as usual".
A damming report by the Commons health select committee, which described young people's mental health service as "unfit". highlighted a "wholly unacceptable" practice by which children sectioned under the Mental Health Act are being held in police cells, due to the lack of beds.