Dozens of 999 calls to Stoke Heath Prison

The ambulance service, which covers Shropshire, all of the West Midlands and Staffordshire, was called out to Stoke Heath, near Market Drayton, 35 times.

The call-outs were for a variety of reasons including assaults, strokes and overdoses.

HMP Oakwood, the UK's largest prison based in the south Staffordshire village of Featherstone, just off the M54, had the most call-outs with 257. This figure included 40 in September and 30 last month.

Oakwood's neighbours HMP Featherstone had 176 call-outs during the same period while Brinsford, the young offenders' institute on the same site, had 21.

Featherstone's busiest month was in May when WMAS was called out 30 times.

Aside from Oakwood, the prison with the most frequent call-outs was HMP Hewell, in Redditch, with 190. Winson Green in Birmingham was not far behind with 161.

HMP Stafford, which houses paedophile Rolf Harris, had 113 call-outs, while HMP Dovegate, in Uttoxeter, had 122.

Others include 43 calls to Long Lartin, 35 to Swinfen Hall near Lichfield and 26 to Drake Hall – the women's prison near Eccleshall.

A Prison Service spokesman said: "We will never compromise on the safety of those in our care, and staff are trained to respond to emergency situations in a timely, appropriate manner.

"Ambulance call-outs are made by healthcare professionals when they identify risks. However, a significant number are for non-violent incidents, including where they attended as a precaution and when the situation was resolved by prison staff."

However there is a separate way to look at the figures, which takes into account prison population. These show that Oakwood, the worst in terms of base call-outs, is actually in line with the region's average. With a population of about 2,000, the 257 call-outs equate to 13 per cent of prisoners – also the Midlands average for category C prisons.

With a population of 677 and 176 call-outs, these figures make worse reading for Featherstone as the calls equate to 26 per cent of prisoners.

A spokeswoman for G4S, which runs HMP Oakwood, said: "This data is meaningless unless you account for the size of the prison population at each facility. On that basis Oakwood is exactly in line with the average for category C prisons in the Midlands."

The figures, obtained through a freedom of information request, also show what WMAS is being called out for.

Of the 1,179 calls 669 were for chest pain – including 189 at Oakwood.

The second highest was 220 call-outs for traumatic injuries.

Oakwood again topped the numbers with 52.

Other reasons included abdominal pain, allergies, back pain, breathing problems, burns, cardiac arrest, convulsions, headache, heart problems and 14 suicide attempts.

These figures come at a time when prisons in the UK are faced with unprecedented levels of violence and a shortage of staff.

Liz Truss MP, the government's justice secretary, has pledged an extra 2,500 prison officers and new security measures to tackle drones, phones and drugs and help make prisons places of safety and reform.

West Midlands Ambulance declined to comment on the number of call-outs they received.