Former Whitemoor inmate talks of the rise in Islamic radical violence in British prisons

John Shelly, who has spent time in more than 40 jails, including Whitemoor, told the BBC he had seen a change in recent years.

He spoke out following a warning by a security specialist who said that staff shortages were making it harder to tackle religious extremism.

Mr Shelly said: “There’s been a real sort of noticeable change of people becoming radicalised and getting themselves involved in violent situations - and being coerced into doing that by some of what you might call the more prominent Muslims that are inside for various offences.”

Mr Shelly, who was released from prison a few months ago after serving a 15 year sentence for armed robbery, said prisoners would often “join the extremists” because they were promised protection.

He claims to have seen prisoners plotting acts of terror as well as endorsing groups such as the Islamic State and al-Qaeda.

“Extremism - it’s grown by the day and they’ve found themselves in a situation where they can’t separate anyone because wherever they separate them to they’re just mixing them with other people who have the same view and same sort of message,” he said.

The Justice Select Committee recently criticised the Government for cutting the number of prison officers by almost 30% - a reduction of 12,530 staff in a four year period up to 2014.

It is claimed this led to a deterioration in safety with fewer staff to monitor inmates.

Chris Phillips, former head of the National Counter Terrorism Security Office, has warned that staff shortages means extremists are not properly monitored.

But Justice Secretary Chris Grayling rejected the claim saying prison overcrowding was at its lowest for a decade and there had been increased spending on measures to prevent radicalisation.

There are more than 12,000 Muslims in jails across England and Wales, according to official data, which shows that more than 100 Muslims are in prison for terrorism offences in Britain.