Prison officers are to be given canisters of synthetic pepper spray to combat violence in jails, Prisons Minister Rory Stewart has said.
The PAVA spray has been trialled in four prisons, and will not be rolled out to all jails which house male prisoners, he said.
The news comes ahead of a speech by Andrea Albutt, the President of the Prison Governors Association, in which she is expected to accuse the Government of failing to respond quickly enough to the jail safety crisis.
Speaking to The Sun, Mr Stewart said trials of the PAVA spray had already shown positive results, without the officer needing to use the spray.
He said: "The mere fact that an officer is wearing the canister on their belt acts as a deterrent and can prevent incidents getting out of hand.”
He added that the decision to arm prison officers with the spray had come following "serious thought", but that safer prisons "are vital for all of us".
He said: "Our prison officers are doing one of the most important and heroic jobs in our society. We must give them the means to do their job."
The prisons system has been under intense scrutiny after levels of violence, self-harm and drug use behind bars surged.
At the PGA's annual conference on Tuesday, Ms Albutt will paint a bleak picture of the state of jails, pointing to "horrendous" quarterly statistics on violence.
She is expected to say: "We have crumbling prisons and an inability to give a safe, decent and secure regime to large numbers of men and women in our care due to lack of staff, not fit for purpose contracts and a much more violent, disrespectful, gang and drug affiliated population."
The Ministry Of Justice said it acknowledged the challenges prison officers faced, and that it had taken meaningful action to address them.
John Podmore, a former governor at the high-security Belmarsh Prison in London, said prisons were best run on co-operation and that the pepper spray would worsen the current "culture of conflict".
He told BBC Radio 4's Today it was part of a "downward spiral", adding: "The POA are already now asking for tasers. What next? Sidearms, rifles in conning towers on perimeters?"
Asked whether officers should be able to defend themselves against violent prisoners, he added: "Good luck with one can of pepper spray against half a dozen prisoners.
"There is talk of this being a deterrent, I think for many prisoners it will be a challenge and there is a real risk the pepper sprays will be turned on the officers."
However, Phil Taylor, the former governor of Wormwood Scrubs, said he accepted it as part of wider reforms, praising the Ministry of Justice for ending its "inertia" on prison violence.
He told Today: "At the moment as well as unlocking 1,200 prisoners in Wormwood Scrubs this morning I suspect there may very well be more than one prison officer injured this morning through some level of assault placed on them.
"Whilst I think it's a regrettable step perhaps, I don't think it's a retrograde step.
"I think it's a much wider picture that we need to consider and it's fair and proper that prison officers should be protected."