Non-Muslim inmates in several of Britain's category A prisons are being forced to pay a 'protection tax' to radical Muslim prisoners out of fear of facing violence.

The 'tax', known as 'jizya', was found to be enforced by some Islamist extremist prisoners in four of Britain's largest prisons.

The shocking findings were uncovered by a team of government investigators, appointed by justice secretary Michael Gove last August to establish the threat posed by Islamic extremists in prisons.

The 'tax', known as 'jizya', was found to be enforced by some Islamist extremist prisoners in four of Britain's largest prisons, including Belmarsh prison (pictured)

The investigation suggests that religious extremists in prison are using bullying tactics and violent threats to force prisoners to convert or pay money.

Tobacco and other luxury commodities smuggled inside prisons are often used by non-Muslims to pay the tax, while some victims said they had to ask friends and family for money.

One Whitehall source told the Sunday Times that the tax may have been inspired by the actions of ISIS, who are well known to demand jizya from non-Muslims living in Syria and Iraq.

'It sets a dangerous precedent and sends a message to non-Muslim inmates that Muslims are going to run the prison according to their own rules and sharia,' the Whitehall source said.

Although no allegations of bullying and demanding jizya have been made against him, Belmarsh prison has perviously held several high profile radical Muslim clerics including Abu Qatada, who was held before he was deported to Jordan

Faced with the option of paying up or suffering at the hands of the radicals, some prisoners have been pressured into converting to Islam to ease their time in prison.

The investigation team examined four Class A prisons, Belmarsh, Long Lartin, Woodhill and Whitemoor, holding a total of 2,633 prisoners.

'People at times are bullied and intimidated and harassed into becoming a Muslim and, if they don't, are attacked,' Steve Gillan, general secretary of the prison officers' association.

He said: 'There is a massive issue about radicalisation and extremism and, to be fair, the prison service is trying to address it.. Will it go away? No. I think the assumption is that it will get worse.'