The use of force in a young offender institution has increased almost 10-fold in just 17 months, inspectors have said.

Campaigners warned the "extremely high" use of force at Ashfield young offender institution near Bristol, largely as a result of a failure to obey staff instructions, has "chilling echoes" of the death of Gareth Myatt in 2004.

The 15-year-old boy was the first child to die while being restrained in custody when he choked to death at the Rainsbrook Secure Training Centre near Daventry, Northamptonshire, in 2004.

Frances Crook, chief executive of the Howard League for Penal Reform, said: "The use of restraint at children's prison Ashfield has gone up by nearly nine times within a year. This jail has a history of failing children and the public. It was not so long ago that this prison was so unsafe that unprecedented emergency measures were implemented and prisoners were withdrawn as it was likely that the management would lose control of the prison."

Inspectors who visited the prison, which holds more than 330 boys aged 15 to 18, found force had been used almost 150 times a month in the 12 months to October last year, compared with an average of just 17 times a month at the time of the last inspection in May 2010.

Force should only be used as a last resort "when there is an immediate risk to the safety of a young person or others or of serious damage to property" and "should not be used simply to obtain compliance with staff instructions", the inspectors said.

But in five of the preceding six months, "failure to obey staff instructions was frequently recorded as the issue leading to the use of force", it was mostly used when moving young offenders to activities, and "the use of force was extremely high," the inspectors said.

A 50% increase in the prison's population since the last inspection, and better recording of incidents, were also behind the rise in the use of force, the prison bosses added.

The Prison Reform Trust campaign group called for the Ministry of Justice to end the routine strip searching of children in custody. Juliet Lyon, the group's director, said: "Routine strip searching of vulnerable boys is unjustified, cruel and abusive in itself.

"If they are to turn around the lives of the teenagers entrusted into their care, staff working with this challenging age group must be equipped with the skills needed to manage difficult behaviour effectively without recourse to punitive sanctions and physical force."