Police files that were opened up with the aim of helping to protect children from sex offenders are being sold for as little as £37 to employers who simply want to find out more about job applicants.

The Criminal Records Bureau (CRB), an executive agency of the Home Office, was set up six years ago to carry out checks on prospective employees whose work would bring them into contact with children and vulnerable adults. Its declared aim is to identify those unsuitable for such work.

But a Sunday Times investigation has established that the CRB is passing files to more than 50 recruitment agencies and corporate investigators which check the background of people applying for jobs that may have nothing to do with children or other vulnerable groups.

Some offer unlawful checks of potential business partners and staff, ranging from web designers to clerical workers. The disclosures mean further questions for Jacqui Smith, the home secretary, already embroiled in a row over the loss of criminal data.

Last week Paul Cavadino, the chief executive of Nacro, a charity that works to reduce crime, called for an inquiry into the trade in CRB records. He said: “The law is clearly being flouted in some cases and it is outrageous that it has been allowed to happen.”

One of the agencies accredited by the CRB — the United Criminal Records Bureau — offers criminal record checks for potential employees for £37. For an extra £5 it can supply an enhanced check that may include unproven police intelligence.

Operating out of a detached house in Bexleyheath, Kent, it claims to scrutinise thousands of police records each year. When approached last week by an undercover reporter asking for information about medical sales staff, it offered checks on a range of employees “as long as you are willing to pay upfront”.

Meena Thiagarajan, a director of the company which operates United Criminal Records Bureau, recommended enhanced checks for administrative staff who were handling confidential company documents. “Whatever they’ve done in their entire life will come up on their enhanced disclosure,” she claimed.

She said an employee’s agreement should be obtained for a request for the file but admitted that she did not obtain original documentation, such as a passport, to check the validity of the application. The reporter did not follow up her offer by submitting an application.

When confronted by The Sunday Times, Thiagarajan said all applications were carefully checked and she would not have submitted an unlawful one. In some cases enhanced checks on administrative staff were justified, she said.

The CRB was established under the Police Act 1997, which stipulates that checks be confined to those working with children and vulnerable adults, and some specific jobs such as police officers, lawyers and accountants. It was launched in March 2002 with the objective of improving access to criminal records in the interests of public safety.

The owner of another CRB-accredited agency, who asked not to be identified, said legal checks on credit card ratings, mortgage details and driving records were routinely checked for job applicants. She said some companies were also offering unlawful checks on criminal records, with a complete background check costing as much as £100.

“It’s easy to abuse the system,” she said. “You can get almost anyone’s criminal record because there are no proper checks to ensure you’re complying with the law.”

At least some of the information held by the CRB appears to have been sent to companies overseas. The CRB lists one company on its website, Personnel Profile Specialists Ltd (PPSL), at a residential address in Upminster, Essex, but its head office is in Auckland, New Zealand.

The PPSL website states: “PPSL are unique in New Zealand as we are the only organisation with an office in the UK registered to access records from the Criminal Records Bureau . . . this has proven exceptionally useful to our clients.”

Richard Peach, who owns the company, said it was not currently accredited by the CRB but had always complied with rules when checking British criminal records.

The law was a “grey area”, he said. But he believed a criminal record, once in the public domain, should be accessible.

Other companies accredited to check criminal records, according to the CRB website, include Kroll and Control Risks, two international security companies, which offer employee-screening services. There is no suggestion that any of their checks has been unlawful.

Many employees are worried by the ease with which dubious or borderline checks can be made because of the minor misdemeanours and unproven allegations that can be unearthed. In one case, the subject of a complaint to the information commissioner, a CRB search revealed the theft of a packet of meat worth 99p in 1984 when the person involved was 16.

Nacro now gets about 20,000 calls a year from people with concerns about the CRB system, including unlawful checks, compared to about 7,000 a year when it was first launched.

A CRB helpline offers little support. One caller who complained of an unlawful check last week was told there was little the CRB could do to help, even though it was accepted by the telephone operator that the rules appeared to have been broken. “If you don’t comply, obviously they will not employ you,” the caller was told.

In a landmark case Derek Howman, 46, from Weaverham, Cheshire, who was fired from his job as a gardener at a residential home after an enhanced CRB check, is taking legal action. He claims the check, which revealed two spent offences, was unlawful. He is seeking compensation.

His case is backed by the information commissioner, who concluded that the CRB check appeared to be unwarranted.

Nacro says it would prefer new a system where employees in the caring professions are vetted by a licensing authority without the criminal records being sent to employers.

The Home Office stated that agencies could have their accreditation removed if they carried out improper checks.

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