A 10-year-old was among more than 300 children suspected to have mental health problems who were held in police cells, i t has emerged.
The youngsters were taken to cells to be assessed rather than medical facilities last year, with some 17-year-olds detained for more than 24 hours, according to the BBC.
The number of detentions in cells of under 18s under the Mental Health Act was 385 in 2011, 317 in 2012 and 305 in the first 11 months of 2013, the BBC said a Freedom of Information request had revealed.
The data, obtained by Radio 4's the World This Weekend, reported a Gwent 10-year-old was taken to a cell as no bed was available.
A police officer may take a person to a "place of safety", which includes locations such as residential accommodation provided by social services or a police station, to protect the individual or others for up to 72 hours.
They are assessed to understand if treatment or care is required.
Health Minister Norman Lamb has previously suggested children should only be taken to cells in "exceptional circumstances".
But asked if there had been 305 exceptional cases last year, Mr Lamb told the BBC: "Absolutely not, no, and we know the position around the country is very variable."
He insisted every area should have arrangements and agreements in place for youngsters and also older people in "very, very exceptional circumstances", adding it was unacceptable for them to be put into police cells at "a moment of acute mental illness".
Mr Lamb said it was not about money but usually proper coordination and collaboration of services.
On ending the use of police cells, Mr Lamb said it could be done and some parts of the country needed to achieve the same standards as those areas which do not use them.
He went on: "We're spending a load of money on these services but in too many places they are not coordinated."
Sarah Brennan, chief executive of the Young Minds mental health charity, also told the BBC: "I think this is really shocking. For children and young people this is a terrible situation and they definitely should never be kept in police cells as an alternative.
"They need to have appropriate care in the appropriate setting and that should never be in a police cell when they have mental health problems.
"For this still to be the situation two years on is a terrible indictment to the slowness of how we react and cope with situations like this."
Chief Constable Simon Cole, the Association of Chief Police Officers lead on mental health, said: "Put bluntly, the issue is often there's an inability to source accommodation for under 18s where they can be readily placed."