Nearly 200 people have been wrongly accused by the Criminal Records Bureau of having criminal records.
The bureau makes 2.5m checks every year
The names of 193 people were mistakenly linked with convictions held on the police national computer (PNC), BBC Radio Five Live has learned.
In some cases the names of those being vetted by the bureau were similar or identical to those of actual criminals.
In others, the criminals had given someone else's personal details to the authorities to avoid a police record.
The Criminal Records Bureau, which came into operation in March 2002, does background checks on those who work with children or vulnerable people.
It was planned as a "one-stop shop" to give employers details about an individual's convictions and cautions, as well as intelligence on them gathered by police.
The names are checked against the police national computer and in this instance the mistakes were made between January last year and February this year.
A Home Office spokesman told BBC News Online the bureau had processed 2.66 million checks last year, and the errors represent a "tiny percentage" of its work.
"These very few instances have occurred because in some cases individuals may have similar if not identical personal details to people who may have a criminal record, and the process errs on the side of caution," he added.
The mistakes of the Liverpool-based agency, emerged in response to a written question from Mark Oaten the Liberal Democrat Home Affairs spokesman and MP for Winchester.
Home office minister Hazel Blears responded: "The CRB has matched 193 disclosure applicants to conviction information held on the PNC, which have subsequently been found to be incorrect."
David Davis, the shadow home secretary, told BBC News Online: "From these new revelations, it is absolutely clear that the quality control of the information held on police computers is inadequate.
"There is serious need for a review of the effectiveness of the system both for innocent people wrongly accused and also to ensure protection for the public from anybody that might be missed as a result of the same failures."
CRIMINAL RECORDS BUREAU
Prior to launch, it emerges 60% of police records on which the CRB will depend are inaccurate
Six months after launch, hundreds of pupils have the start of their school term delayed after demand for teachers' certificates exceeds expectations
Minicab drivers are also stopped from working because delays mean they cannot renew their licences
The predicted costs of handling three million applications over 10 years has risen from £250m to £400m
The CRB says up to 85% of employers were expected to apply for checks by phone - but over 80% applied on paper, which takes longer
The CRB is now able to process 50,000 every week - all within six weeks of application
The bureau was beset from the start by problems and delays.
For instance, hundreds of pupils had the start of their school term in September 2002 put back because it had failed to provide certificates for teachers.
But the Home Office told BBC Radio Five Live that the bureau has drastically improved with 84% of checks carried out in three weeks.
Between January 2003 and February this year the bureau had more than 31,000 applications over three weeks-old outstanding.
The Home Office spokesman told BBC News Online there was a clear process in place to enable people to challenge any CRB findings.
Anyone working for a school or care home who finds themselves wrongly accused will receive a copy of the alleged charge as will the establishment where they have applied.
Fingerprinting at a police station may also be necessary for further identification.