A senior civil servant has been suspended over the Home Office's failure to update police records of Britons convicted abroad.
Records of 540 serious offenders were not put on the system
Some 27,000 case files, including 540 for serious or violent offences, were not put on the police computer.
The Home Office said an official had volunteered evidence to an internal inquiry in the last 48 hours, and was suspended pending an investigation.
A spokeswoman said the information warranted a disciplinary inquiry.
She would not name or say how senior the suspended official was, but the BBC has learned it is a senior civil servant.
The First Division Association, which represents the interests of the UK's senior public servants, has confirmed they are "working with a member" over the disciplinary action.
Home Secretary John Reid launched an internal inquiry after coming under repeated fire for the episode. It is expected to take six weeks.
He has also instigated a root-and-branch review of Britain's criminal databases.
His spokesman said Mr Reid was writing to Cabinet colleagues to get agreement for a review of British databases which received information about criminality, and how information was recorded on them.
BBC correspondent Robin Brant said the home secretary was seeking to full review of how information on criminal databases in the UK is recorded and shared.
John Reid has ordered a review of criminal databases
This includes systems such as the police national computer, the Criminal Records Bureau and lists of football hooligans, as well as the way information is shared and exchanged between the UK, the rest of the EU and other countries.
He also wants to review how to respond to the information when it is received.
Senior sources have told the BBC that Mr Reid's next priority is to get the police and probation services to assess and, if necessary, provide supervision for those offenders whose crimes were not logged on the police computer who are deemed a risk.
Lord Chancellor Lord Falconer told the BBC that the mistakes were now being corrected.
He said: "We took much to long to deal with it. It should have been dealt with much, much more quickly.
"There are no excuses for that. But the problem is being faced and there is a solution currently being unrolled."
Meanwhile, minister Joan Ryan is to meet EU counterparts in Dresden to discuss improving systems for sharing information.
She is expected to ask for biometric information, such as fingerprints, to become part of the data on criminals passed between EU governments.
Mr Reid and his ministers Ms Ryan and Tony McNulty have insisted they were not told of the backlog in notifications of British criminals' European convictions or police requests for resources to clear it.
But they have accepted that meetings took place between department officials and the police about the problem.
The Association of Chief Police Officers (Acpo), which now has responsibility for updating police records, sent a letter to Mr McNulty in October warning of the difficulties in processing notifications.
That was passed on to Ms Ryan, who has responsibility for the Criminal Records Bureau.
Earlier, it was confirmed that four drug offenders and a people smuggler had passed Criminal Records Bureau checks to work with children or vulnerable adults.
But no violent or sexual offenders appear to have slipped through the net.
And it is now thought that about 70 of those 540 serious offenders not logged on the system have been convicted of a further offence since returning to the UK.
The head of the National Association of Probation Officers, Harry Fletcher, said others may have disappeared, changed their names or gone abroad again.