Terror fears over unvetted visitors who are free to roam jails

Members of the public are appointed to check that prisons and immigration centres are running safely.

They can speak to convicts without supervision and have unrestricted access to any detainee.

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However, security checks on up to 1,800 members of the Independent Monitoring Boards have not been kept up to date, a leaked letter reveals.

Members are supposed to have full security checks every three years. But only one check has been taking place, when they are appointed.

Inquiries to make sure they have not been radicalised, or could be passing information to dangerous convicts, have not been made since.

Details emerged in a letter to senior IMB members, written by head of secretariat Norman McLean.

It says: "The current position regarding security clearances throughout the prison estate, including IMBs, has traditionally been that a person would usually be security cleared on first appointment but, thereafter, no further security checks were carried out.

"A similar policy has operated in IRC (immigration removal centres) for staff and IMB members.

"You will, I hope, appreciate that in these days when we must be even more careful about national security, that policy cannot be permitted to continue."

A review of the clearance given to all members is now taking place, starting with those given full counter-terrorism clearance to visit jails such as Belmarsh, the high security prison in South East London.

Shadow Home Secretary David Davis said: "This has severe implications for our security. These establishments do not just hold normal offenders. They hold some of the most dangerous people in the country including terrorists who want to do real harm."

The Ministry of Justice said: "The Prison Service takes security very seriously and all personnel that have unrestricted access to prisons are assessed for their suitability to do so."

At least 4,000 illegal workers cleared in a security blunder have still not been banned from taking sensitive security jobs.

The Security Industry Authority has missed its own deadlines for revoking licences that allow people to become bouncers and bodyguards.

Home Secretary Jacqui Smith disclosed last month that the Agency had written to over 10,000 suspects warning their permissions would be withdrawn in 42 days.

Terror fears over visitors who are free to roam jails

Some foreign nationals are spending a year in detention at a cost of £43,000 each, because the Government hasn't sent them home, the prisons watchdog has warned.

Anne Owers, chief inspector of prisons, said the procedures for deporting foreign criminals remained "chaotic" following the mistaken release of 1,000 inmates who should have been considered for removal.

Prisons often learned at the last minute the Government was planning to deport an offender, her annual report said.

They were moved on to immigration removal centres --but in many cases there were delays in sending them home.

At least 90 spent a year in the centres at a cost of £43,435.

Attempts to build a way out of the jail overcrowding crisis may be nothing more than an "expensive and insubstantial life raft", she added.