Prison populations (inmates per 100,000 population)

US: 700 Portugal: 130 England and Wales: 125 Libya: 125 Scotland: 120 Spain: 115 China: 110 Germany: 95 Italy: 95 Belgium: 85 France: 85 Ireland: 80 Sweden: 65 Saudi Arabia: 45

The director general of the Prison Service, Martin Narey, said the situation is now "critical".

Mike Newell, chairman of the Prison Governors Association, said magistrates courts should no longer have the power to send offenders to jail.

Liberal Democrat home affairs spokesman Simon Hughes called on the government to heed the warnings and said many people in prison should not be there at all.

'Severe strain'

Mr Narey said in the last three weeks there has been an "utterly inexplicable rise" in the prison population of about 600 prisoners a week.

"And that in a period during which the Home Office statisticians told us there would be no rise in the population at all.

"That's put us under very severe strain," he said.

Numbers in jail are at a record high

He said he, the home secretary and the Lord Chief Justice have said they want short sentenced prisoners, who do not need to be locked up, to be given community sentences.

"But still we're getting this very, very significant increase in the use of custody and it is putting us under considerable strain."

Mr Newell agreed that too many of those who had committed less serious crimes were being locked up, and that short sentences were worthless and clogged up the system.

"The effect of too many prisoners is slow but extremely damaging, and turns us back to where we were many years ago."

He said vital work to prevent reoffending was being put in jeopardy, as staff were having to concentrate on keeping their overcrowded institutions safe.

"If magistrates are not going to use their powers properly they should be stripped of them," he said.

Crisis meeting

The prison governors have demanded an urgent meeting with Home Secretary David Blunkett to discuss the crisis.

A Prison Service spokeswoman said the prison population in England and Wales had reached a record high of 69,689 on Thursday and was expected to top 70,000 on Friday.

Prison sentences this year

About 3,000 since 1 January About 400 per week 400 prisoners fills a medium-sized jail

Simon Hughes said: "Many short sentences do no good, either to the prisoner or to society. Many very long sentences run out of much of their effectiveness after more than ten years.

"Overcrowding has a direct and adverse effect on the chances of rehabilitation and on preparation for life after jail.

"There are still many people in prison who ought not to be there. An effective community sentence can be much more useful than many of the periods spent inside."

Ministers 'anxious'

BBC correspondent Niall Dickson said recent growth in the numbers of people being sent to jail has been "both steep and remarkable".

About 3,000 people have been sent to prison since the beginning of this year - equivalent to about 400 every week.

Ministers are understood to be anxious that tougher community sentences are given for less serious crimes.

And unless politicians can convince the courts to sentence fewer people to prison, some drastic action will be needed.

That could mean that options previously ruled out by the government, such as the use of army camps or mass early releases, may have to be reconsidered.