The number of children in custody has hit a record low five years after the start of a programme designed to limit the use of prison, according to statistics released by the Ministry of Justice today.

When the programme Out of Trouble, run by the Prison Reform Trust, began in September 2007 there were 2,835 children under 18 in custody in England and Wales. By May 2012 that number had fallen 38% to 1,740. Over the same period, the number of young adults (18 to 20-year-olds) in prisons fell by approximately 10%, while the number of adults rose 7% to 85,913 from 80,216. Figures for May 2012 show 1,744 under-18s in custody, down 296 on the same month last year.

The figures were released today in advance of an address to be given this evening by the justice secretary, Kenneth Clarke, at a reception celebrating Out of Trouble’s work.

The programme, designed to reduce the number of children and young people in custody, is working with 12 youth offending teams (YOTs). It works with YOT staff and defence lawyers to improve practice and look at ways to reduce breach and reoffending. Between 2008/9 and 2010/11 it delivered a 38% reduction in the number of children sentenced to custody, compared with a national average reduction of 33% over the same period.

The Prison Reform Trust puts the national reduction in detained children down to a combination of factors, including a fall in the number of children coming before the courts and a reduction in overall crime and serious youth crime between 2008 and 2010. It also highlights the benefit of greater engagement between the Youth Justice Board and youth offending teams with the courts, and legislative changes to how courts sentence under-18s.

The trust’s director Juliet Lyon said: ‘The surest way to guarantee the adult prison population of the future is to lock up children and young people.’

Lyons said lessons from the way the treatment of children has changed could be used to inform the treatment of other vulnerable groups, to help reduce the number of women, older teenagers and people with learning disabilities or mental health needs who are caught up in the justice system.