Chief inspector Anne Owers criticised "deplorable" conditions

The youths were then ordered to clean up their mess in "deplorable" conditions described by the chief inspector of prisons, Anne Owers.

Inmates from Onley Young Offenders' Institution near Rugby in Warwickshire must travel to and from jail in the privately-run prison vans with no toilet facilities, the chief inspector's report said.

The report, published on Wednesday, also said inmates were left shivering in sub-zero temperatures in their cells last winter.

Strip-search concern

It described how inmates aged between 18 and 21 were kept in cells with badly damaged windows in January.

More than 50 damaged windows were found on three wings alone and inmates were seen shivering in "intolerably cold conditions".

The sub-standard cells housed young adult offenders and not juveniles, who are also incarcerated at Onley, the report said.

I am very pleased with the significant progress that has been made at Onley since the last inspection report. Phil Wheatley Prison Service director general

Although the 540-inmate jail had improved significantly since an inspection published last year, the chief inspector of prisons, Anne Owers, said there were some poor aspects which were beyond staff control.

"Onley is clearly a much improved establishment," said Ms Owers.

"There was none of the evidence of routine intimidation of young prisoners by staff that we reported last time and much more evidence of positive work.

"However, levels of force remained high, as did allegations of bullying."

Ms Owers team also raised concerns about forced strip-searches being used on young offenders who may have suffered abuse in the past.

The chief inspector concluded there had been "considerable improvement" overall.

Prison Service director general Phil Wheatley said: "I am very pleased with the significant progress that has been made at Onley since the last inspection report."