Fourteen staff at the Driver and Vehicle Licensing Agency (DVLA) have been dismissed and 101 disciplined after they swapped so many pornographic e-mails that it affected the agency's mainframe computer.
The 14 employees, including one higher executive officer, were dismissed for sending obscene e-mails to people outside the DVLA, which is based in Swansea.
The others, who were given varying degrees of reprimand including final warnings, had sent the material to colleagues within the building.
The action was taken after a three-month inquiry into the controversy at the DVLA, which has 6,000 staff.
A spokeswoman told the Times that the pornography had been downloaded from the internet by staff during working hours. The images were then attached to e-mails that were sent around the building.
Suspicion was raised when computers started slowing down because of the size and number of images being sent. Other members of staff, unaware of what was going on, complained that obscene material was being attached to innocent-looking e-mails.
Managers ordered the investigation and the IT department was able to pinpoint the computers involved.
The spokeswoman said tighter controls had been introduced which would monitor all e-mails with images attached.