Documents obtained by The Daily Telegraph through Britain's Freedom of Information law indicated there were 506,720 requests for various individuals' "communications data," a figure that privacy advocates said showed police had more than enough eavesdropping authority.
"The government should come clean with Parliament and tell us exactly how the powers they currently have been used in the past," said MP David Davis, a former Tory shadow interior ministry and critic of Labor's policies on civil liberties.
The Daily Telegraph report was published as Britain considers a new Communications Bill that the newspaper said will likely include more power authority for police to carry out electronic surveillance.
The government has said the legislation is needed to help catch terrorists, pedophiles and major criminals.
Davis said discrepancies among police departments in the numbers of requests made for surveillance indicated Parliament should think twice about expanding police powers.
"It is frankly not good enough that the government is considering introducing a snoopers' charter without even being able to tell us what they have used communications data for in the past -- and indeed not even be able to tell us how many times they have done so," he said.