A Japanese policeman has been fired after inadvertently leaking thousands of police records over the internet.

The officer, who worked for Tokyo's Metropolitan Police Department, installed a copy of the Winny file sharing application on his work computer.

By not limiting the sharing of files he allowed 6,600 police documents onto the P2P network, including interrogation reports and classified locations of automatic licence plate readers.

"It is no surprise that the Japanese police force has taken a hard line against this officer for disobeying advice about not running P2P file-sharing software on his PC," said Graham Cluley, senior technology consultant at Sophos.

"The authorities have been trying to enforce a ban following a number of similar embarrassing incidents in the past.

"But what this case underlines is the need for all businesses to better control their users' behaviour, and limit the programs they can run on their computers.

"Firms need to ask themselves if their employees have a legitimate requirement to run applications like P2P software, and if not, to control their usage through technology."

The leaked details included personal information on 12,000 people, including 400 members of the notorious Yamaguchi-gumi yakuza, Japan's most infamous organised crime gang, which is currently under investigation for the assassination of the mayor of Nagasaki.