Cuts of some £90 million to prison services in recent years are behind the riots at Maidstone Prison in Kent, the Prison Officers union has told ITV News.
"The reduction in staff numbers means there are fewer prison officers available to carry out a normal prison regime", Prison Officers Association vice chair Ralph Valerio said.
"This means that prisoners spend more time locked up in a contained space.
"That can get to you. Many of the inmates also have anger management issues," he said.
The current staff to inmate ratio at HMP Maidstone is 1:30, which meant the staff had to retreat quickly when the incident, involving up to 180 prisoners, began earlier today, Mr Valerio added.
More top news
The vice minister of foreign affairs criticised the comments as “ignorant”.
Taxes will need to rise to pay for a modernised health service, experts have said.
The son of one of those said to be involved in the theft claims the pair did it “for the thrill”.