By Mark White, Home Affairs Correspondent
Sky News has learned that increasing numbers of British inmates are being bullied into converting to Islam while in jail.
The Prison Officers Association says it is symptomatic of the growing power and influence of Muslim gangs in prison.
However, there are also concerns that some of those converts could be radicalised by more extremist elements in prison.
Sky News spoke to one young woman who said her brother was being bullied by members of a Muslim gang, who were trying to force him into converting to Islam.
The woman did not want to be identified for fear of reprisals against her brother, who is serving a sentence in excess of 10 years in a high security prison in England.
She said: "He just looks like a broken man ... he's tearful on visits. I'm just really scared for him."
She also claimed the bullying had taken a more violent turn: "He's been physically assaulted. He's had black eyes.
"In the showers, he got threatened with a knife. He's not going to back down. He's not going to convert for anyone."
She added: "He just spends his time in hiding in his cell. He's got at least another five years to serve. I don't know how much longer he can hold out."
Official sources acknowledge forced conversions are a problem in the country's prisons.
How large the problem is remains unclear, as inmates are often afraid to report such intimidation for fear of reprisals.
Joe Chapman, a former prison officer who now acts as a prison law consultant, believes the problem is on the increase.
"I think it could be a huge problem. Previously I'd probably only worked in about a dozen or so prisons as an officer," Mr Chapman said.
"But this job takes me to 40 or 50 over the year, throughout the country. It's become obvious to me that it's a growing problem.
"About half a dozen of my clients have directly reported problems with being forced to convert ... those that weren't Muslim when they came in and those that were and have been forced to look at more radical ideas about their faith."
It is the potential route to extremism that will be of most concern to the authorities.
There is no automatic pathway but Jihadist groups do focus on the vulnerable - and new converts in the prison environment offer them a captive audience.
Former Home Secretary Lord Reid told Sky News: "When they arrive in prison, inmates often feel isolated, lacking in identity.
"They don't have family groups and kinships around them. On top of that, very often there's a need for protection, a feeling that you've arrived in prison, you're on your own but there are people who appear like you, who give you a set of beliefs but also the protection of being in a gang.
"It is a very, very fertile ground for recruitment and proselytization and radicalisation in prison."
There are currently around 11,200 Muslims in prison in England and Wales.
That figure is about 13% of the total prison population and is far higher than in the wider community, where Muslims make up less than 5% of the population.
Around a third of Muslim inmates will have converted in prison, but sources say most are willing converts.
Sky News has learned that increasing numbers of British inmates are being bullied into converting to Islam while in jail.
The Prison Officers Association says it is symptomatic of the growing power and influence of Muslim gangs in prison.
However, there are also concerns that some of those converts could be radicalised by more extremist elements in prison.
Sky News spoke to one young woman who said her brother was being bullied by members of a Muslim gang, who were trying to force him into converting to Islam.
The woman did not want to be identified for fear of reprisals against her brother, who is serving a sentence in excess of 10 years in a high security prison in England.
She said: "He just looks like a broken man ... he's tearful on visits. I'm just really scared for him."
She also claimed the bullying had taken a more violent turn: "He's been physically assaulted. He's had black eyes.
"In the showers, he got threatened with a knife. He's not going to back down. He's not going to convert for anyone."
She added: "He just spends his time in hiding in his cell. He's got at least another five years to serve. I don't know how much longer he can hold out."
Official sources acknowledge forced conversions are a problem in the country's prisons.
How large the problem is remains unclear, as inmates are often afraid to report such intimidation for fear of reprisals.
Joe Chapman, a former prison officer who now acts as a prison law consultant, believes the problem is on the increase.
"I think it could be a huge problem. Previously I'd probably only worked in about a dozen or so prisons as an officer," Mr Chapman said.
"But this job takes me to 40 or 50 over the year, throughout the country. It's become obvious to me that it's a growing problem.
"About half a dozen of my clients have directly reported problems with being forced to convert ... those that weren't Muslim when they came in and those that were and have been forced to look at more radical ideas about their faith."
It is the potential route to extremism that will be of most concern to the authorities.
There is no automatic pathway but Jihadist groups do focus on the vulnerable - and new converts in the prison environment offer them a captive audience.
Former Home Secretary Lord Reid told Sky News: "When they arrive in prison, inmates often feel isolated, lacking in identity.
"They don't have family groups and kinships around them. On top of that, very often there's a need for protection, a feeling that you've arrived in prison, you're on your own but there are people who appear like you, who give you a set of beliefs but also the protection of being in a gang.
"It is a very, very fertile ground for recruitment and proselytization and radicalisation in prison."
There are currently around 11,200 Muslims in prison in England and Wales.
That figure is about 13% of the total prison population and is far higher than in the wider community, where Muslims make up less than 5% of the population.
Around a third of Muslim inmates will have converted in prison, but sources say most are willing converts.
