“Tory austerity is squarely to blame for this unprecedented wave of violence and self-harm in our prisons.

“It is a national scandal that there is an assault every 20 minutes in one of our prisons, that a member of prison staff is attacked every hour and that self-harm is at a new record high.

“The Tories need to take responsibility for these failures, but their actions so far have been woefully inadequate. Instead of more tinkering at the edges, at next week’s Budget they should launch an emergency plan with substantial new Treasury funds to tackle the widespread understaffing and overcrowding that has made our prisons a danger to the officers, inmates and wider society.

“Anything less will see prison violence continue to spiral out of control.”