Prison officers in England and Wales are to be issued with canisters of a synthetic pepper spray to help deal with violence and disorder.
The chemical incapacitant known as PAVA has been trialled in four jails and will be carried by officers in all publicly-run prisons for men from 2019.
Prison officers welcomed the move.
But the announcement came as the Prison Governors Association (PGA) accused the government of failing to react quickly enough to a “crisis” in jails.
The decision to introduce the spray at a cost of £2m follows what the Ministry of Justice says was a “successful” six-month trial at Hull, Preston, Risley and Wealstun prisons.
Ministers say the spray acted as a deterrent and it is also thought it helped give staff greater confidence to deal with dangerous situations.
The Ministry of Justice said the spray will only be deployed in limited circumstances when there is serious violence or an imminent risk of it taking place and officers will receive training before being allowed to carry it.
In a speech to the PGA conference, president Andrea Albutt will acknowledge there is a “more positive feel” in jails after staffing levels were increased and security boosted.
But she will say there has been a “subtle campaign” to blame governors for problems and claimed ministers did not have the “humility” to admit their policies – which had included budget cuts – were wrong.
A Ministry of Justice spokeswoman said: “Senior managers in prisons do vital work and we are grateful for their dedication and commitment.
“We acknowledge the ongoing challenges they face and, as the president notes, we have taken meaningful action to address them which is starting to yield results.”