Almost £600m has been spent to check the backgrounds of people who work with children, it emerged last night, 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%, to £35.21.
The result has been that fees paid for CRB checks have more than trebled, from £41m in 2002-03, when the system was introduced, to £131m in 2008-09. Overall, since the system was created the CRB has charged fees totalling £571m.
"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. The Lib Dem peer Baroness Neuberger has accused the government of "trying to create a risk-free society, which we know in our heads and our hearts is impossible".
Willott said she had become concerned about the issue of CRB checks when approached by a constituent, a supply teacher, who needed a CRB check carried out each time she worked for a new local authority.
"Under the current system, job applicants and volunteers can be forced to pay for several identical CRB checks at any one time just because they are applying for more than one job," Willott said.
"Despite the CRB's apparent efficiency savings, the fees for CRB checks have gone through the roof. Delays in the system are getting worse, causing many to miss out on a job offers because their CRB check hasn't come through in time."
A written comment from the Home Office said, "The CRB plays a vital role helping to protect the most vulnerable in our society by giving employers the extra tools they need to make informed recruitment decisions.
"The cost of a CRB check now represents even greater value for money given the protection and assurance that such checks provide. We have recently reduced the CRB fees as part of the CRB Business Plan for 2009/10 from £31 to £26. The change will come into effect from 1 October this year.
"In 2008 a further 18,000 unsuitable people were prevented from gaining access to children and vulnerable adults as a direct result of a CRB check, bringing the total to around 98,000 in the past five years."