Brian Caton, of the POA, says it was only a matter of time before the riot happened
A clean-up operation is taking place at a prison where three inmates were injured and up to 75% of the facility was damaged in a riot lasting 21 hours.
The violence at HMP Ashwell in Rutland was finally brought under control at 2245 BST on Saturday.
The Prison Officers Association (POA) said three staff had barricaded themselves in an office for about 12 hours, waiting to be rescued.
The Ministry of Justice has denied overcrowding was a factor in the riot.
The POA said four accommodation wings, two workshops and a healthcare centre had been "wrecked".
It is thought a decision to remove privileges from some inmates led to a small group inciting others to riot.
Some inmates have been transferred to other sites across the East Midlands, including Lincoln Prison.
Glyn Travis, POA spokesman said: "There's been a very, very serious riot resulting in serious damage to the prison and loss of cellular accommodation.
"On top of that, unfortunately, three members of staff were basically held hostage for the best part of 12 hours.
"The prisoners weren't holding them hostage as such but they had to secure themselves in an office until such time as staff came to their rescue and that must have been very, very traumatic for those people."
POA national executive member Peter Chapple said administration buildings and a reception area were damaged during the violence, which began at 0100 BST on Saturday and had left only about 25% of the category C prison habitable.
The final repair and clean-up bill would run into hundreds of thousands of pounds, he said.
POA national chairman Colin Moses said: "We have been warning of this type of disturbance for many months, but no one wants to listen."
He said a lack of investment had led to fewer specialist staff, and a failure to address the issue could lead to HMP Ashwell becoming the "first of many disturbances of 2009".
But Justice Minister Lord Bach said he did not believe the incident was linked to staffing or budget issues.
The Prison Service said no staff were injured, while there were minor injuries to three prisoners.
The prison, built on a former Army camp, started as an open prison in 1955 and was converted to a Category C jail in 1987.
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