HM Prison Oakwood: Ambulance called nearly every day
Ambulances were called to England's largest prison, the privately run Oakwood, more than twice as often as any similar jail last year.
Staff at the category C establishment, run by G4S, requested an ambulance 358 times in 2013, the BBC has discovered.
A G4S spokesperson said the figures did not accurately present the full picture.
And the Ministry of Justice said there were "national processes" to ensure prisoners' safety was not compromised.
But some staff at the jail, near Wolverhampton - which experienced a major disturbance earlier this month - say officers tend to be over-cautious following a hard-hitting report in the wake of a death at Oakwood last year.
BBC Radio 4's The Report asked all ambulance trusts in England how many times they had been called to Category C male prisons in 2013.
All but the North East region replied.
Information from West Midlands Ambulance Service NHS Foundation Trust revealed that staff at Oakwood called ambulances at a rate of almost one a day - more than double that of HMP Wymott in Leyland, Lancashire, from where the second-most calls were made.
North West Ambulance Service NHS Trust was called 148 times to Wymott, which houses 1,178 prisoners - more than 400 fewer than Oakwood.
"The ambulance here is so regular," one Oakwood inmate told the BBC.
"I've never seen it before in any prison I know. It's partly because they haven't got 24-hour healthcare [at Oakwood], which they need. But they've got the facilities for 24-hour healthcare. They're not used, not once."
A G4S spokesperson said: "Because healthcare facilities differ at prisons, the figures do not give an accurate representation of the position. We follow national processes which are in place for staff so that they can respond to emergency situations in a timely and appropriate fashion."
There are facilities on site to enable the £241m prison to provide 24-hour healthcare to prisoners, but they have not been used since Oakwood opened in April 2012.
A 2013 report by the prison's Independent Monitoring Board explained: "The whole top floor of the healthcare unit remains mothballed due to [Oakwood's] change in status from Cat B to Cat C when commissioned."
According to the Ministry of Justice, category C prisoners cannot be trusted in open conditions, but are not considered to have the resources and will to make a determined escape attempt.
Category B prisoners are deemed to be more "difficult", requiring a higher level of security, though not the maximum.
Although Oakwood's capacity of 1,605 inmates would help to explain a large number of callouts, it also had the second-highest ratio of callouts to prisoners.
Blantyre House, in Kent, had the highest, but houses only 122.
Prison custody officers working at Oakwood have suggested that the circumstances surrounding the death of an inmate at the jail in February 2013 may help to explain the high number.
A report by the Prison and Probation Ombudsman on the death, caused by a heart attack, has not been released to the public, but the BBC has seen a copy of its findings.
In it the ombudsman states: "I am particularly concerned about the poor standard of the emergency response. It took too long to begin resuscitation and staff did not have access to, nor had they been trained to use, automated defibrillators."
The report also outlines how there had been "unacceptable confusion and delay" in calling an ambulance.
It was more than an hour after finding the prisoner unresponsive that an emergency ambulance was called.
The ombudsman's findings also reveal the lack of experience of many of the staff at Oakwood, something confirmed to The Report by serving prison custody officers at Oakwood.
One staff member explained that they did not start cardiopulmonary resuscitation (CPR) "as it had been such a shock to see [the deceased]", while another said they had not started CPR because they had "panicked".
An unnamed custody officer at Oakwood told the BBC that following this incident staff were reluctant to take any risks with prisoners and were overcautious in calling the ambulance.
Prisoners also took advantage of the staff inexperience by feigning illness to get a break from prison routine, the officer said.
Last year Oakwood was given the lowest performance rating possible by the Ministry of Justice.
Responding to the figures, Sadiq Khan, shadow justice secretary, said: "This is taxpayers' money being used to send ambulances to prisons.
"You would have thought that as the government is trying to make savings, you'd like to address that. It should trigger many, many questions."
A prison service spokesperson told the BBC: "We do not compromise the safety of prisoners, and national processes have been established for staff to respond to emergency situations in a timely and appropriate fashion."
Hannah Barnes's report on Oakwood prison can be heard on BBC Radio 4 at 20:00 on Thursday, or afterwards on the iPlayer