The number of prisoners in England and Wales reached a new all-time high today. There were 82,319 inmates in total, nearly 140 more than the previous record set in February.
A Prison Service spokeswoman said it included 12 inmates being held in police stations as part of emergency measures to deal with overcrowding, known as Operation Safeguard.
The number of inmates has rocketed by nearly 600 in just three weeks - the equivalent of an average-sized jail.
The figures came after a row with the Prison Officers Association (POA), which claimed its members had lost control of sections in some jails, leading to "no-go areas".
Shadow justice secretary Nick Herbert said: "The Government can hardly be surprised that prison numbers have risen when violent crime has doubled in the last 10 years.
"They have ignored every warning about the lack of cells, overcrowding has got worse and re-offending has risen.
"The right way to reduce the prison population in the long term is not by releasing prisoners early or shortening sentences, but by ensuring adequate jail capacity, reforming prison regimes, reducing re-offending and cutting crime."
The Director of the Prison Reform Trust, Juliet Lyon, asked: "How can a Government committed to reducing social exclusion continue to allow prison numbers to slide out of control without taking steps to reduce sentence lengths, cut any unnecessary use of remand and recall and provide treatment in the community for addicts and the mentally ill?"
The Prison Service spokeswoman said: "The prison population remains of concern, but we have brought forward measures to address this which have already had an effect.
"Since the beginning of March we have increased total capacity by over 1,000 places through the prison building programme and more efficient use of the estate.
"This means we are able to manage the current high level of the population more effectively, with little use of police cells under Operation Safeguard.
"However, we are not complacent, and expect the pressure to continue for the time being."
She added: "We commend the hard work of prison staff in holding prisoners safely and securely.
"Protecting the public is our first priority, and we will always ensure that there are places for those serious and dangerous offenders who ought to be in prison."
More than 2,500 new jail places would be delivered during this year, she added.
The POA's Glyn Travis appeared to accept that prison officers had lost control of jails, admitting that there were "no-go areas" in some institutions where inmates have "complete control".
Asked on BBC Radio 4's Today programme whether it was the case that "prison officers are not in control of our prisons, prisoners can do pretty much what they like - including escape - but they don't want to escape because life is so cushy", Mr Travis replied: "Unfortunately, you have summed that up pretty much well accurately."
A Ministry of Justice spokesman said: "The comments by POA undermine the excellent work done by prison officers - their own members.
"It is simply not true that there are areas of prisons that are no-go areas for staff.
"Prisoners do try to escape, but the Prison Service has an excellent record in preventing such escapes.
"The POA's description of prisons is out of touch with reality."
He went on: "Prisons have fundamentally been stable for over 10 years - this is an excellent record which all staff should be proud of."
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