An EU directive forcing ISPs to keep internet data on customers for one year officially comes into force in the UK.
The start date of the EU directive was three weeks ago, but today the UK government officially implements the legislation.
The directive means that all ISPs will have to hold data that determines communications between individuals, but is not supposed to store the content of emails and websites.
Keeping the data has meant extra costs of 48 million to ISPs, which the government has agreed to cover, the Home Office confirmed to IT PRO.
In a statement, the Home Office said that the government's priority was to protect public and national safety.
It said: "Communications data is the where and when of communication and plays a vital part in a wide range of criminal investigations, and prevention of terrorists attacks as well as contributing to public safety more generally.
"Without communications data resolving crimes such as the Rhys Jones murder would be very difficult if not impossible."
Any access to communications data was governed by the Regulation of Investigatory Powers Act 2000 (RIPA), the Home Office claimed.
This was supposed to ensure that effective safeguards were in place, and that data was only accessed when it was necessary and proportionate to do so.
The EU Data Retention Directive has passed by without much fuss.
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