Jeremy Hunt is right to advocate the importance of work experience for politicians as well as managers in the NHS; the health secretary really should try a night in the cells. It would utterly convince him of the need to end the practice of using cells to detain mentally ill children and adults who are waiting for a psychiatric assessment.

Is it conceivable that a 13-year-old child with a suspected broken leg would be held in a police cell if there was no orthopaedic surgeon ready to assess them? Yet on 25 occasions since the start of this year that is, in effect, what has happened to children felt to have an acute mental disorder, in Devon and Cornwall. On three occasions those children were aged 12 or 13. Custody suites are scary places, especially at night and unacceptably so for an acutely distressed child.

It is not the fault of the police, who go to great lengths to try to arrange for psychiatric assessments to take place in an appropriate place of safety, after they have used their powers under section 136 of the Mental Health Act.

These powers allow them to detain a person in a public place, whom they believe may have a mental disorder posing a risk to themselves or others, in order to take them to a suitable place of safety for an assessment. The home secretary has made it clear that police cells should only be used in exceptional circumstances, and yet in Devon and Cornwall alone, 674 assessments have taken place in police custody and only 277 in medical or psychiatric settings since January.

Nationally, 22,000 people were subject to a section 136 last year. The vast majority did not go on to compulsory hospital admission, and it is clear that with better access to community mental health teams many of these assessments could be avoided in the first place. There are long-term implications for anyone who may have to declare that they have been subject to compulsory detention; despite all the efforts to reduce stigma, it is hardly a reference.

Once in custody, the lack of doctors, who must be approved under section 12 of the Mental Health Act, to carry out the further assessments which usually take place out of hours, causes further delays. These delays however are expensive for the police rather than the health service, so there is little financial incentive for the NHS to change their practices, even though it is clearly a distressing ordeal for the person under detention.

Too often health professionals are doing the "system's business", rather than what is right for patients when it comes to caring for those in the community with mental illness. Carers sometimes find it impossible to arrange assessments for family or friends, if a GP, for example, refuses to see someone unless they ask for help themselves (difficult if a person is paranoid and doesn't recognise that they are unwell). Specialists may refuse to assess without that GP referral, and so no assessment takes place until there is an acute crisis and the police are called.

If an individual does need to be admitted to hospital following a section 136 assessment, they then face delays through the lack of available beds. In the last month in Devon and Cornwall alone, four people were held in police custody for such long periods of time that a bed provisionally booked was no longer available once the ambulance arrived to transfer them. The Care Quality Commission has found that in over 50% of psychiatric wards there was 90% bed occupancy and in 15% of wards in excess of 100% occupancy. For children the situation is dire, with almost no provision for assessment in an appropriate medical setting, let alone in-patient beds.

Inadequate funding allocated to mental health services and a failure to provide timely support for this vulnerable group is also placing great strain on the police.

If "parity of esteem" for mental illness is to have any meaning, the secretary of state must insist that there is an immediate end to the use of police cells to assess people in acute distress. Many areas have already achieved it but if there are still 13-year-old children being assessed in police cells in 2014, parliament must act to make it illegal.