Swiss police have secretly tracked the whereabouts of mobile phone users via a telephone company computer that records billions of movements going back more than half a year, a Zurich newspaper has reported.

The revelation in the SonntagsZeitung newspaper triggered objections from politicians and the country's privacy ombudsman about high-tech snooping on citizens who like the convenience of a mobile phone.

Officials from state telephone company Swisscom confirmed the practice, but insisted information about mobile customers was only handed out on court orders.

"Swisscom has stored data on the movements of more than a million mobile phone users. It can call up the location of all its mobile subscribers down to a few hundred meters and going back at least half a year," the paper reported.

"When it has to, it can exactly reconstruct down to the minute who met whom, where and for how long for a confidential tete-atete," it said.

Some 3,000 base stations across the country track the location of mobile phones as soon as they are switched on, not just when customers are having conversations, it said.

Prosecutors called the records a wealth of information that helped track criminals' movements.

"This is a very efficient investigation tool," Renato Walti, an investigating magistrate in Zurich who specialises in organised crime, was quoted as telling the paper.

The paper said Swisscom and law-enforcement officials were reluctant to discuss the records, which were supposed to be secret.

But it quoted Toni Stadelmann, head of Swisscom's mobile phone division, as saying: "We release the movement profile of mobile telephone customers on a judge's order."

SonntagsZeitung said there was no legal basis for storing such information.

"Secretly collecting data is highly problematic," added Alexander Tschaeppat, a judge and member of the lower house of parliament.