His views emerged as the prison population yesterday soared to 47,006 - 12 over the network's certified capacity - and as the Prison Service agreed that the potential for disturbances increased with overcrowding.
Derek Lewis, director general of the Prison Service, said the system could now only 'manage the risk' of riots - not eliminate it.
But he emphatically denied that he was appealing to Michael Howard to pull back from his policy, which will lead to more people going to jail, because the prisons could not cope.
He said: 'The message is a simple statement of fact. Our job is simply to provide custody for those sent to us by the courts.'
He said that contingency plans, including the use of Army camps, police cells and temporary accommodation within existing prisons, were in hand to take any surplus prisoners.
He was speaking following a damning report by Judge Stephen Tumim, the Chief Inspector of Prisons, into the riots which tore apart Wymott prison in Leyland, Lancashire, months ago.
Judge Tumim said the jail was 'close to anarchy', yet earlier warnings of impending trouble - including one from his inspectorate the year before - had gone unheeded.
One of the triggers of the disturbances, which reduced the showpiece jail to a shell with a cost in the region of pounds 20m to rebuild it, was a sudden and massive influx of prisoners following overcrowding in other jails in the North-west. Some are currently holding 50 per cent more people than they should.
The riots at Wymott last September were the latest in a line of disturbances in similar low security Category C prisons which shared common problems of having to hold unsuitable, volatile young offenders, poor staff-prisoner relationships, mounting drug problems and bullying and violence.
In a speech last night in Bristol, Judge Tumim warned of further strife. He said many prisoners described as Category C came from organised inner-city drug gangs, who could dominate inside jail.
'It follows that there is a serious risk of future disturbances in Category C prisons of this kind, which are in effect large camps or warehouses without real control.
'New prisons will take time and money before they can be built . . . Overcrowding is again the prime cause of anxiety for those who have to run our prisons,' he said.
Judge Tumim's report was seized upon by reform groups and opposition parties who urged Mr Howard to rethink his claim that 'prison works'.
It underlined the fears expressed by judges and prison governors who have taken issue with Mr Howard since he announced his 'get tough' policy at the Conservative Party conference.
Mr Howard yesterday accepted Judge Tumim's warnings that trouble could break out in other prisons. He said: 'The circumstances at Wymott were not unique and continuing vigilance will be required to avoid the repetition of such wanton destruction.'