Its concerns were raised in a report into "purposeful activity" behind bars.

BBC: Prisoners 'watching too much TV'

"We do know that higher rates of purposeful activity are associated with lower risks of self harm and death by suicide, " Mrs McCabe said.

BBC: Hydebank lock-up blamed for suicide of Allyn Baxter

But Brig Munro said the regime did not motivate or encourage young offenders to get out of bed and take part in purposeful activity.

BBC: Polmont, Falkirk

The overcrowded conditions mean Welsh prisons also failed to meet the recommended average of 24 hours a week of purposeful activity for each prisoner.

BBC: Jail crowding worse than ever

However, they said relationships between staff and prisoners remained mutually respectful and there was found to be much more purposeful activity and a greater focus on resettlement.

BBC: NEWS | UK | England | Kent | Prison shows 'marked improvement'

Meanwhile, the number of inmates taking part in "purposeful activity" at the jail had increased from 60% to 75%, with the latest report describing this as a "significant achievement".

BBC: Addiewell Prison

There was very little opportunity for purposeful activity.

BBC: Hydebank lock-up blamed for suicide of Allyn Baxter