Peter McParlin, chairman of the Prison Officers Association, has accused the Ministry of Justice (MoJ) of over-reacting to a violent jail incident involving Woolwich murder suspect Michael Adebolajo.
Five prison officers have been suspended following the apparent restraint of Adebolajo on Wednesday. All "strenuously deny" any wrongdoing.
Mr McParlin told BBC Radio 4's Today programme: "We have spoken to our members and on the basis of what our members have told us they have done absolutely nothing wrong. We are concerned that the Ministry of Justice have over-reacted due to the notoriety of this prisoner."
He also criticised the MoJ for failing to "correct false reporting" of the incident at Belmarsh.