Shrewsbury Prison 'is second most overcrowded'
Shrewsbury Prison is the second most overcrowded prison in England and Wales, the Prison Reform Trust says.
The prison, which was built in 1877 to hold 170 inmates, now houses 326.
The trust said nearly two thirds of prisons were operating at overcrowded levels, making it harder for staff to work "intensively" with offenders.
A spokesman for the Prison Service said jails provided acceptable levels of accommodation but accepted some were overcrowded.
The spokesman added: ""We are aiming to reduce the existence of crowding alongside reducing the cost of the prison estate."
HMP Shrewsbury became a category C training prison for vulnerable prisoners in January 2010.
The most overcrowded prison, according to the report, is HMP Kennet in Liverpool, which was designed to hold 175 men but now holds 337.
A Prison Reform Trust spokesman said: "For people in prison themselves, overcrowding has a tangible impact.
"Figures for 2010/11 show that nearly a quarter of people in prison are being held in overcrowded accommodation, either doubling up in cells designed for one occupant or being held three to a cell in cells designed for two people."
The organisation is an independent charity.