A former prison governor has said the Government should consider sending the army in to stabilise prisons.
Ian Acheson said an appeal should be made to experienced staff who have recently left to return and form a "task force", adding the army could form part of a package of extra resources to restore order.
The suggestion comes after the head of the body representing governors warned that prisons in England and Wales are in crisis after "perverse" Government reform and a "toxic mix" of pressures.
Mr Acheson, who previously led a probe into radicalisation in jails, told BBC Newsnight: "There's clearly a limit, in terms of the number of violent incidents taking place at any one time, and if you cross that limit you will have very serious problems across the whole prison state, and that must be avoided at all costs.
"I think in relation to an effective response to the prisons that are the most concerning, what I would suggest the Secretary of State does is very seriously consider an appeal to staff who have left recently, experienced staff, through voluntary exit schemes, to create a task force to go back into those prisons causing the most concern.
"And get back control and create a regime and create stability. If that is insufficient, I would go as far as to say, and there is a precedent for this back in the 1990s, but if that isn't sufficient I would suggest that you need extra resources sent in to prison simply to stabilise them short term, and you could consider for example using the army for that."
BBC News said he told Newsnight: "There is a systemic and widespread instability in prisons and unless it is tackled, I really do fear that we're going to see a member of staff killed on duty."
Earlier, Andrea Albutt, president of the Prison Governors Association (PGA), launched a blistering attack on the Ministry of Justice (MoJ), saying its members had been left "devastated at the complete decline of our service".
In an open letter published as riot officers were called to a prison for a second day, the governor said a recent increase in indiscipline among inmates is "of grave concern".
The Government has said it has taken "immediate action" to increase prison officer numbers while creating a new body to drive through its reform programme.
However Ms Albutt said members had told her that they have seen "nothing tangible" come from the MoJ to ease the burden on prisons, leaving governors facing "unacceptable stress and anxiety" on a daily basis.
"We know many prisons are in crisis and I deliberately use that term, because it can't be dressed up in any other way," she said.
The governor warned an unforeseen rise in prisoner numbers had left the estate with "virtually no headroom" in spaces, while seasonal pressures were adding strain to limited staffing levels.
Specialist teams were called into HMP The Mount in Hertfordshire for the second day on Tuesday after inmates reportedly seized control of part of a wing, while HMP Erlestoke in Wiltshire also saw an incident involving prisoners.
"The instability we are seeing is clearly linked to a poor regime," Ms Albutt said.
"Further loss of accommodation, like those lost during the current, ongoing incidents at The Mount over the last couple of days, means drafts of prisoners are being moved across the country, compromising the Families Pathway and destabilising the receiving prisons as they try to maintain order amongst disaffected displaced men.
"This toxic mix does not have a quick fix and the future looks like more of the same."
The governor said the issue of prison officer recruitment remained "critical", with a net increase in the number of prison officers in 2016/17 of just 75.
However she also raised concerns that a drive to increase the number of officer numbers too rapidly may cause further issues.
Members of the PGA have warned that the selection process was allowing "many unsuitable people through" while training was of "poor quality".
According to the PGA there are currently 40 "prisons of concern", of which 10 are "very concerning".
A spokesman for the MoJ said: "We know that our prisons have faced a number of long-standing challenges, which is why we have taken immediate action to boost prison officer numbers and have created Her Majesty's Prison and Probation Service."