The home secretary, Charles Clarke, will make a fresh push to compel internet and phone companies to retain their records of traffic on millions of private emails, text messages and mobile phone calls for up to three years at an emergency meeting of European security ministers on Wednesday.
Critics say the scheme will generate such a mountain of data - enough to fill 10 stacks of files reaching from Earth to the moon - that it would take the security services 50 years to run one search.
The plan emerged as Mr Clarke made it clear yesterday that he was resisting calls to rush through other new counter-terrorism legislation, such as the creation of a special UK border force. The government plans to introduce new legislation this autumn, including the creation of a conspiracy offence of "acts preparatory to terrorism".
In the face of a claim by the former Metropolitan police commissioner, Lord Stevens, that there had been eight planned terrorist attacks in Britain in the past five years, Mr Clarke confirmed that "there were attacks which were thwarted" but declined to give any details.
But he warned: "Our fear is of course of more attacks until we succeed in tracking down the gang that committed the atrocities on Thursday."
In a BBC interview, he also refused to disclose whether he had issued further control orders on suspected terrorists in the immediate aftermath of the bombings in addition to the 11 already in force.
The communications surveillance plan, being put forward by Britain and France, means companies would have to keep, for a minimum of 12 months and a maximum of three years, details of all the traffic and location generated by private mobile phone calls, text messages and emails. It will involve agreeing a common standard across Europe on how long telecommunications data should be kept.
The National Crime Squad appealed to British telecommunications and internet companies on Friday to preserve email messages in case they proved useful in the investigation.
Mr Clarke stressed that the compulsory scheme would not mean spying on the content of any email or text message: "Telecommunications records ... which record what calls were made from what number to another number at what time are of very important use for intelligence. I am not talking about the content of any call but the fact that a call was made." Much of the data are kept for billing purposes, but only for a short period.
David Blunkett dropped the proposal in 2003 after opposition from the internet industry and his son Hugh, a computer professional.
Britain and France floated it again earlier this year, but it was rejected in May by the European parliament's civil liberties committee, who said it would generate a mountain of data that would be unsearchable: "If all the traffic data covered by the proposal did indeed have to be stored, the network of a large internet provider would, even at today's traffic levels, accumulate a volume that is equal to 4m kilometres worth of full files - that is in turn equal to 10 stacks of files each reaching from Earth to the moon."
The committee estimates that this system will cost each large firm £120m to set up and £16m a year to run and some medium size internet firms will not be able to carry the burden.
Its report, published in May, says that terrorists could easily avoid being traced by using front men to buy telephone cards, by switching between mobile phones from foreign providers, using public telephones or by using internet companies outside Europe.
Mr Clarke will appeal to the European parliament to drop its opposition in the wake of the London bomb attacks.
Shami Chakrabarti, the director of the group Liberty, said she supported the principle of standardising the retention of communications data but she wanted the safeguards to be standardised as well.