The president of the Prison Governors Association is to warn of a "serious risk" of disturbances in jails because of a shortage of resources.
According to Paul Tidball, prisons in England and Wales are in a "crippling, vicious circle".
He is also concerned over proposals to change the way jails are managed.
The Ministry of Justice said measures to introduce efficiencies in the prison system would not be agreed unless they passed "safety and decency" thresholds.
Mr Tidball's comments will be made in a speech to be delivered at the annual conference of the PGA.
He will say new prisons are being built at "great" expense, and that existing prisons are "starved" of resources to pay for the new ones.
As a result, he claims, they are less effective at preventing reoffending - meaning that more prison places are needed.
And Mr Tidball will warn that attempts to impose efficiency savings through modernising working practices will increase the risk of prisoner violence.
"The loss of a prison or two through disorder," he will say, "could wipe out the savings at a stroke."
The PGA represents almost 1,300 prison governors across the UK.
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