The calls, which are stoking long standing privacy fears, were made at a hearing convened on Tuesday by a House subcommittee that is chaired by Rep. James Sensenbrenner, a Republican congressman from Wisconsin. Four years ago, Sensenbrenner proposed, and then quickly withdrew, legislation calling for mandatory data retention for ISPs.

In prepared testimony for today's hearing, Jason Weinstein, deputy assistant attorney general at the Justice Department, said that data retention , especially online child pornography.

Current policies that only require ISPs to preserve usage data at the specific request of law enforcement authorities are just not sufficient, Weinstein said. Increasingly, law enforcement authorities are coming up empty-handed in their efforts to go after online predators and other criminals because of the unavailability of data relating to their online activities, Weinstein said.

"There is no doubt among public safety officials that the gaps between providers' retention policies and law enforcement agencies' needs, can be extremely harmful to the agencies' investigations," he said in written testimony.

In many cases, ISPs are already collecting and maintaining "non-content" records about who is using their services and how for business reasons, and for handling issues such as customer disputes, Weinstein said. Those same records can be extremely useful in criminal investigations too, he said.