A GROUP of current and former prisoners are planning to sue the Government over alleged exposure to harmful radon gas at Dartmoor Prison.

The group, already numbering 450, claims the Ministry of Justice had been aware since 1987 that inmates could have been exposed to the gas yet no effective measures were taken to protect their health.

Prisoners and staff were kept in the dark about the risks of the odourless gas which can cause lung cancer.

The first public admission from the authorities that radon could be a problem came when the MoJ closed the Princetown prison last summer. All inmates were transferred to other prisons, to allow work to reduce radon exposure to be carried out.

However, many doubt the prison – dating back to 1809 – will ever reopen, as it is built from, and rests on, granite, a rock which constantly emits radon.

Many prisoners have reported suffering poor health, with three prisoners being diagnosed with cancer, possibly linked to radon exposure in their cells.

One former prisoner, detained for two and a half years in Dartmoor, believes his health problems may be due to, or at least exacerbated by, exposure to radon during his time there.

The ex-inmate, who is remaining anonymous as he remains out on licence, describes having been constantly breathless in prison. He was sent from Dartmoor to an open prison in a wheelchair and was expected to need end-of-life palliative care. However, since leaving HMP Dartmoor his health has improved.

The group has written to the Prime Minister, seeking an apology and compensation.

The former inmate said: “The prisoners were kept there in unsafe conditions for years without ever being informed of the hazard. Indeed, they still haven't been! It's not unlike the early days of the sub-postmaster scandal."

Despite awareness of radon radiation in Dartmoor, referenced in a Commons debate in 1987, monitoring the gas only began in 2010, the year the Ministry of Justice first publicly acknowledged its presence in the prison.

It then began monitoring, but very few test results have been made available.

The former inmate has joined the group action being handled by Kesar Solicitors in Bristol seeking a government apology and compensation.

The ex-prisoner said that his cell was not well-ventilated and the only window was unreachable and plastered shut as was the ventilation air brick. He said radon levels were never measured while he was at the prison.

“I literally had to plead to get transferred from Dartmoor,” he said. “Some prisoners on the ground floor landing complained vociferously of breathing problems, all the time carrying their NHS oxygen cylinders on the back of their prison wheelchairs.

He added that he only became aware of in recent recently about the presence of radon at the prison through media reports.

The group’s legal team is seeking legal aid to help fund the case.

An MoJ spokesperson said: “After close monitoring of the situation at HMP Dartmoor, we took the decision to temporarily close the site. We continue to take advice from specialists to explore how it can be reopened as quickly as possible.”