Home Secretary Charles Clarke said he would raise the issue on Wednesday at a meeting of European Union interior ministers which he has called in Brussels to discuss a joint response to the bombings by suspected Islamist militants.

"We believe that telecommunications records, whether of telephones or emails, which record what calls were made from what number to another number at what time, are of very important use for intelligence," Clarke told the BBC.

"I’m not talking now about the content of any call, but the fact that a call was made. And we believe it’s important to get a retention of data, of what calls were made, for some considerable time."

Phone records are likely to play an important role in the probe into Thursday’s attacks by suspected al Qaeda-linked bombers who killed more than 50 people aboard three London underground trains and a bus.

TIME AND LOCATION

Mobile phone data show not only what numbers are connected to each other via calls, voicemail and text messages, but also the time and the physical location of the parties within the cell network when a given conversation took place.

Clarke did not specify how long telephone companies and Internet service providers could be required to store data, although The Observer newspaper said the proposal was for "several years".

Five EU governments -- Britain, Germany, Spain, France and Italy -- agreed in principle last March that the retention period should be raised to one year.

At present, storage rules vary around Europe but records are typically kept for about three months and destroyed after the customer has been invoiced. Retaining them for longer would impose extra costs on telecoms providers.

European investigators have complained of cases where records have already been deleted for data protection reasons by the time police request them. They say this is a particular problem in complex and lengthy probes.

But keeping records for longer would meet fierce resistance from civil liberties groups and data protection officials, particularly in countries such as Germany, who argue this amounts to a form of Big Brother-type snooping.

"There’s no evidence that that level of national surveillance is warranted. I believe it’s disproportionate," said Simon Davies, director of lobby group Privacy International.

"It will result in a very high level of false accusations and unnecessary scrutiny of people’s private communications."