The government has defended safety measures at Lewes jail after prison service chiefs were criticised over a riot on Tuesday night.
A report praised the prison this year
One member of staff needed treatment for minor injuries after about 30 inmates went on a rampage.
The Prison Officers' Association blamed staff cuts and the mixing of adult prisoners and young offenders for the disturbance, which led to damage in two wing offices, the flooding of a wing and broken windows.
A local MP said the prison was "a tinderbox waiting to be set alight", claiming the staff-to-prisoner ratio was too low.
A Prison Service spokesman said: "Whatever the population pressures, the Government is uncompromising in its response to serious and dangerous offenders.
"Where there is a need to protect the public, this will take place in a secure environment.
"The prison estate can accommodate over 66,000 prisoners in an uncrowded capacity and a further 10,000 prisoners without compromising safety.
"We have already made £60m available to provide an extra 740 places by March 2004, on top of funding for an extra 2,320 places in 2002/2003."
Lewes MP Norman Baker had said the long-term problem faced by Britain's prisons was in having 70,000 prisoners in 2003 compared with 10 to 15 years ago when there were about 40,000.
He said: "Lewes, like many other prisons in the country, has too many prisoners, not enough staff and is quite frankly a tinderbox waiting to be set alight."
An internal investigation is under way at the prison.
Home Office figures show the number of inmates at Lewes prison exceeds the comfortable level by eight prisoners but is within the safety limit by more than 20.
The prison had been praised this year in a report by the Board of Visitors for improvements in suicide prevention and drugs.