Lockdown restrictions and staff shortages are to blame for attacks on jail staff doubling since March, a prison officer has claimed.
The officer, from HMP Dartmoor in Devon, said he feared a colleague would be "severely injured or killed" due to a lack of resources in the jail.
He told the BBC levels of violence had got "much worse" and staff felt "unsafe" when pressured to open cells.
The Ministry of Justice said it was investing £2.75bn to improve prisons.
HMP Dartmoor saw assaults on staff double in the six months after coronavirus restrictions were introduced in March, a report from HM Inspectorate reveals.
During that period there were 12 assaults on staff, four of which were considered "serious", compared to six non-serious assaults in the previous six months.
The officer, who wishes to remain anonymous, said: "This year, due to the pandemic and exasperating emotions among prisoners, we've had more violence than what we've had at Dartmoor for many years.
"Earlier in the year we had a prisoner punch a member of staff in the nose and attack another three officers, one of them being female, who he struck in the face.
"Just in the last couple of weeks we had some prisoners fighting on a wing, an officer tried to break it up, and he was rendered unconscious. It really is escalating."
Assaults on prison staff across England and Wales fell by 17% from quarter one of 2020 (January to the end of March) to quarter two (April to the end of June), according to data taken from the Prison Service incident reporting system.
However, annual figures for England and Wales showed a 242% increase in attacks on officers between 2012 and 2018, from 2,987 to 10,203.
The Dartmoor officer said a notice of closure handed to the prison in 2013 had seen it "starved of resources".
The Prison Officers Association (POA) said fewer than 30 officers were regularly monitoring more than 600 prisoners at Dartmoor.
"It never seems enough, it just feels so unsafe and we're just having pressure put on us all the time from our managers to get the prisoners out when it feels like we shouldn't be," the officer said.
'Go off any minute'
He added a lack of funding for security measures, including cameras and scanners, meant he feared "either an officer is going to get severely injured or killed".
The POA said assaults on staff had been "exacerbated by coronavirus as well as low staffing numbers".
An ex-prisoner recently released from the Category C prison said violence had "tripled" over the past three years.
"The tension is so big, it could go off at any minute," he told the BBC.
A Ministry of Justice spokesperson said: "We are investing £2.75bn to improve prisons and increase security, and giving staff body-worn cameras, police-style restraints and PAVA spray to allow them to do their jobs more safely.
"Violence against our hardworking staff will never be tolerated and we will always push for the strongest possible punishment."