According to the Prison Officer's Association (POA), the assault of prison officers at HMP Whitemoor in Cambridgeshire was "vicious" and "cowardly".
On 9 January, two inmates at the high security prison attacked a prison officer from behind with improvised bladed weapons. The officer suffered stab wounds to his head, chest and face. Other staff members intervened and in the end, five were taken to hospital.
The two prisoners involved were wearing fake suicide vests during the incident.
The Metropolitan Police are treating the incident as a terror attack.
Steve Gillan, General Secretary of the POA, said: “I have received a full briefing on this cowardly and vicious attack and there is no doubt inmy mind that but for the bravery of staff then this morning we could have been talking about the death of a Prison Officer at Whitemoor Prison."
A prison service spokesman said the incident on Thursday was "quickly resolved", but did not state the nature of the officer's injuries.
Counter-terrorism officers are currently investigating the attack.
"Now is the time for government and employer to work with the POA to restore control, order and discipline in the prison service," the Prison Officer's Association said.
No arrests have been made at this time.
The Metropolitan Police said: "At this early stage of the investigation, we are keeping an open mind with regards to any motives and enquiries to establish the full circumstances of the incident are ongoing."
All five injured prison officers have been discharged from hospital.