Thousands of people are potentially having their mobile and laptop data seized at Britain's borders under little known terrorism legislation, reports the Telegraph.
The police power to seize gadgets or copy the data on them is so broad that the police do not even have to justify to travellers why they are doing it.
David Anderson QC, the appointed independent reviewer of terrorism laws, is now expected to raise concerns over the power in his annual report this week.
He is apparently going to call for "proper checks and balances" to ensure the power is not being abused.
With police powers to "stop and search" on the streets, police have to work within a framework to justify searches and seizures of property, and property can only be taken if there is an arrest.
This isn't the case for powers being used at air and seas borders. Anderson told the Telegraph: "Information downloaded from mobile phones seized at ports has been very useful in disrupting terrorists and bringing them to justice.
"But ordinary travellers need to know that their private information will not be taken without good reason, or retained by the police for any longer than is necessary."
Up to 60,000 people a year are "stopped and examined" as they enter or return to the UK under powers contained in the Terrorism Act 2000.
But is not known exactly how many are having their phone or laptop data seized.
A Scotland Yard spokesman said: "Under the Terrorism Act 2000 a person may be detained and questioned for up to nine hours to determine if that individual is a person concerned in the commission, preparation or instigation of acts of terrorism as outlined in the Act.
"As with any power to detain an individual it is used appropriately and proportionally and is always subject to scrutiny by an independent reviewer of UK anti-terror laws."