Internet service providers are to keep records of emails and online phone calls under controversial new government regulations that come into force today.

ISPs will be legally obliged to store details of emails and internet telephony for 12 months as a potential tool to aid criminal investigations. Although the content of emails and calls will not be held, ISPs will be asked to record the date, time, duration and recipients of online communications.

The new regulations are contained in an EC directive on data retention that already applies to telecoms providers and is now being extended to ISPs.

The directive was conceived as a response to the London bombings of July 2005, following which the Council of the European Union highlighted "the need to adopt common measures on the retention of telecommunications data".

"Knowing when someone sent an email or made an IP telephony call, and knowing who they emailed or called, is very revealing information - these regulations potentially put that information in the hands of a wide range of public bodies," said Sam Parr, a lawyer specialising in communications at Baker & McKenzie.

Shami Chakrabarti, the director of Liberty, said this was "nowhere near as disproportionate and terrifying" as government plans for a central database of communications information, which she believes poses a greater long-term threat to civil liberties.