The prison population in England and Wales has reached more than 76,000 for the first time on record.
The prison population has been rising in the past few months
For the third consecutive week the number of people in prison has reached an all-time high - up 158 on last week to 76,035, the Home Office said.
Earlier, the Prison Service said the total was 75,058 five months ago, followed by a seasonal dip to just over 74,000 after Christmas.
It has said capacity is about 77,000, and will rise to 80,000 in three years.
Previously the prison population hit a high in April 2004 of 75,544 inmates.
It had begun to fall, before rising in the past few months.
The Prison Reform Trust estimates the prison population has risen by about 25, 000 over the last 10 years.
Trust director Juliet Lyon said: "The increase was not because of any appreciable rise in crime but due instead to tougher sentencing, tougher talk by politicians and scaremongering by the populist press.
"The net result is a grossly overcrowded prison system, poor conditions, a chronic lack of purposeful activity and appalling reconviction rates."
Ms Lyon said numbers would continue to rise until alternatives to prison for petty offences, such as fines and community sentences, were used more readily.
She also called for improved treatment programmes for drug addicts and mental illness sufferers.
But a Home Office spokeswoman said: "We constantly monitor the prison population, which fluctuates on a daily basis.
"Although the prison population has reached an all-time high, the National Offender Management Service is able to manage this.
"Whilst the prison population has risen sharply in the last few weeks, growth has been slow over the last 14 months."
She added that 2,600 new prison places were opened last year.