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.
More top news
Outbreaks of rain in the southwest will spread across Wales and central and southern England this evening and overnight
Owen Smith has been sacked from Jeremy Corbyn's shadow cabinet after calling for a new EU referendum.
Scotland Yard says the seat will be preserved as potential crime exhibit in the investigation into the attempted murders.