London: Almost £600 million (Dh3.68 billion) has been spent to check the backgrounds of people who work with children, it emerged yesterday, triggering claims the vetting system is in danger of spiralling "out of control".

There are now concerns that, owing to a combination of rising fees and increasingly laborious bureaucracy, potential volunteers and employees are being deterred from working with children and vulnerable adults.

According to figures released to the Liberal Democrats by the Home Office, the number of Criminal Record Bureau (CRB) checks in England and Wales has almost tripled from £1.4 million in 2002-03 to £3.85 million in 2008-09.

The increase in the volume of applications has been matched by the rising cost of processing the background checks, which are paid for by employers, the self-employed and, in the case of volunteers, by the government.

In the past three years, the fee for a "standard" background check has risen by more than a third to £25.18, and for an "enhanced" check for those in charge of children by 45 per cent to £35.21.

The result has been that fees paid for CRB checks have more than trebled, from £41 million in 2002-03, when the system was introduced, to £131 million in 2008-09. Overall, since the system was created, the CRB has charged fees totalling £571 million.

"The government is allowing CRB checking to run out of control," said Jenny Willott, the Lib Dem's Cabinet Office spokeswoman.

"Checking criminal records of people working with children and vulnerable adults is essential. But when the system is so clumsy and costly that it starts putting people off, there is something seriously wrong."

The government pledged to tighten the rules governing background checks for those working with children following the murders of the schoolgirls Jessica Chapman and Holly Wells by their school's janitor, Ian Huntley, in 2002.

But now there are concerns that employers, charities and organisations are being penalised by an overly bureaucratic public protection system at a time when there is a shortage of people working with children and vulnerable people.

The increased number of applications for background checks has created delays in processing job applications. In 2008-09, nearly 400,000 people had to wait more than a month for their enhanced check, more than double the previous year. The revelations are likely to provide further ammunition for critics who accuse the government of heavy-handed public protection measures.