The Prison Reform Trust said jail populations are growing out of control
The 20 most overcrowded jails in England and Wales have been named by the Prison Reform Trust.
Shrewsbury jail - which has 178 places in use but holds 326 inmates, meaning it is filled to 183% of its capacity - is the most over-subscribed jail.
Juliet Lyon, of the Prison Reform Trust (PRT), said: "Ministers have grown complacent about jail overcrowding."
The Ministry of Justice said the figures did not show that prisons operated at unsafe levels.
Using Ministry of Justice figures, the PRT said almost two-thirds of prisons are officially overcrowded, and the system holds 10,000 more offenders than it was designed to handle.
Ms Lyon, director of the PRT, said: "The prison population is mushrooming out of control, and the government is still trying hopelessly to build its way out of a crisis."
She added: "It will take a concerted effort across government to reserve prison for those who have committed serious and violent crimes and to invest in drug treatment for addicts, mental health and social care and enforced community work for petty offenders."
Prisons minister David Hanson said: "The figures published by the Ministry of Justice and reproduced in part by the PRT do not show any prison operating beyond the safe level agreed by prisons and area managers.
"We will always provide enough prison places for the most dangerous, violent and persistent offenders."
According to Ministry of Justice figures, the top 20 most overcrowded prisons in England and Wales are:
1. Shrewsbury (at 183% of capacity)
2. Swansea (177%)
3. Leicester (173%)
4. Preston (171%)
5. Dorchester (165%)
5. Lincoln (165%)
5. Usk (165%)
8. Altcourse (161%)
9. Canterbury (160%)
9. Durham (160%)
9. Exeter (160%)
12. Bedford (158%)
13. Northallerton (157%)
14. Wandsworth (152%)
15. Doncaster (146%)
15. Winchester (146%)
17. Bristol (145%)
17. Cardiff (145%)
17. Forest Bank (145%)
17. Lancaster (145%)