The failure to update police records of Britons convicted abroad has not led to any violent or sexual offenders being cleared for work, the Home Office says.
Home Secretary John Reid said he wanted to reassure the public
Fears had grown that some offenders may have been cleared to work with children after failures to record EU convictions with the Criminal Records Bureau.
Home Secretary John Reid said he wanted to "reassure the public" that he was working "to ensure public protection".
The issue concerns 27,500 files which were not logged on a police computer.
Five of the 540 most serious offenders had sought checks with the CRB for employment purposes which did not show up their crimes, the Home Office said.
A spokeswoman confirmed that four of these had been convicted for drugs offences in Europe. The other had been convicted of assisting illegal entry to a country.
She confirmed that two were applying for jobs as sports coaches, two had sought employment as carers and one as a foster carer.
Four were men and one was a woman, she said.
"These offences would not in themselves have necessarily debarred them from the employment that they sought," she added.
The Home Office said it is now informing the offenders' places of work of the new information.
It is thought about 70 of the 540 criminals have been convicted of a further offence since returning to the UK.
The head of the National Association of Probation Officers, Harry Fletcher, said the figure, based on probation officers' research, was particularly low as half of all offenders are usually expected to reoffend within two years.
"It seems very low but that may be because many of them have disappeared, changed their names or even gone abroad again," he added.
Shadow home secretary David Davis called Mr Reid "out of touch" and said the announcement would not quell people's fears.
More cases probed
A further nine cases had been found where individuals with similar details to those on the list had undergone CRB checks.
Efforts were continuing to establish whether they were actually the same people, the spokeswoman added.
None of the offences committed by this group were of a violent or sexual nature.
In a statement, Mr Reid said: "I have authorised these details to be released to reassure the public that the necessary steps are being taken to ensure public protection."
He added that he has asked the police and probation services to ensure that any sex offenders identified would be monitored in the same way as they would if they had been convicted in the UK.
Unaware of backlog
The 27,500 figure was calculated by the Association of Chief Police Officers (Acpo) when it took over responsibility for processing the data from the Home Office in March last year.
That emerged publicly only earlier this week.
The home secretary said he was unaware of the backlog.
Of the 540 most serious cases, which include rapes, murders and paedophilia, 260 have now been entered onto the police national computer.
The Home Office has also dismissed reports in the Observer newspaper that a "fresh blunder" had been committed which left details of a gangster's convictions abroad not entered on the police national computer.
Dale Miller, 44, was jailed for violent offences in an EU country and then returned to the UK shortly before 2000, the newspaper said. He went on to kill a rival and was jailed for manslaughter in 2002.
But the Home Office said Miller had been a well-known criminal since 1982 and that a number of his foreign convictions had been on the police national computer since 2001.