All 43 police forces in England and Wales were hit and only 27 were back online four days after the crash. Avon and Somerset police were still denied access over a week later.
The fingerprint system allows police officers to check the prints of suspects against national records or add new records. In the Metropolitan Police area alone, 600 sets of fingerprints are said to be checked every hour. About 20% of fingerprints checked on the system lead to identifications.
The failure raises questions about whether the more complex ID card technology will prove reliable. In April a Home Office report on the fingerprint system portrayed it as a success.
A spokeswoman for the Home Office said this was the first time in six years there had been a failure, but that she was unable to say why back-up systems failed to provide continuity of service.