A difficult, violent and unpredictable prisoner smashed a television set in his cell and attacked four prison officers with shards of the broken glass, a union has said.
The inmate burst through his cell door on the healthcare wing of the G4S-run Birmingham Prison yesterday, attacking three staff who were serving his lunch and those that came to their aid, the Prison Officers Association (POA) said.
All four staff were taken to hospital for treatment, with two suffering serious cuts and one remaining in hospital for surgery on his arm, the POA's Brian Clarke told BBC News.
"A very difficult, violent, and unpredictable prisoner was being served his midday meal at his door," Mr Clarke said.
"He burst through that door and assaulted three members of staff with shards of broken glass.
"He also assaulted a fourth member of staff who came to their assistance and fought violently with the other staff who came along afterwards."
Mr Clarke added: "A television set had been smashed in his cell in a moment of random violence sometime earlier in the day.
"We believe it had been removed but we suspect that the prisoner may have hidden shards of glass in his cell or on his person."
But he also told BBC News the category B Victorian prison - which can hold 1,450 inmates and was taken over by G4S, the firm at the centre of the Olympics security shambles, last year - was "staffed appropriately for a very, very difficult, very, very violent, and unpredictable prisoner".
"This was an unprovoked, unpredicted offence," he added.
News of the attack by the prisoner, who was on remand, emerged as the firm was told it will lose its contract to run the Wolds prison in East Yorkshire from next year and was unsuccessful in its bid to run other jails.
A G4S spokesman said: "G4S has confirmed that four members of staff were injured during an incident at the prison yesterday morning.
"The staff, all members of the prison's healthcare unit, were wounded in an altercation with a prisoner on remand, with two staff receiving serious lacerations.
"All staff were transferred to local hospitals for treatment. The prisoner has been contained."
He went on: "The safety and welfare of our staff and those in our care is our utmost priority, and we have launched an immediate investigation into the circumstances surrounding thisattack.
"Our thoughts are with our staff at this time."