Barclays Plc is being probed by the United Kingdom's privacy watchdog, the Information Commissioner's Office (ICO), over allegations that the British bank spied on its staff, the agency said on Sunday.

Earlier this year, Barclays said it was changing a system that it was piloting, which tracked how employees spent their time at work, after critical media reports accused the bank of spying on its staff.

The ICO said on Sunday a formal probe was ongoing but it could not say when the investigation would conclude.

"People expect that they can keep their personal lives private and that they are also entitled to a degree of privacy in the workplace," an ICO spokesman said.

"If organizations wish to monitor their employees, they should be clear about its purpose and that it brings real benefits. Organizations also need to make employees aware of the nature, extent and reasons for any monitoring," he added.

The probe was reported earlier by The Sunday Telegraph.

In late February, Barclays said it was changing how it used the Sapience software so it would now track only anonymized data, in response to staff feedback that the system was intrusive.

Sapience gives companies "insights into work patterns" and tracks employee productivity by monitoring their computer usage, according to its website.

Such systems are becoming increasingly common among banks and other financial firms, which use voice recognition and other behavior-tracking tools to watch for unusual behavior that could indicate misconduct.

In 2017, Barclays faced widespread criticism when it rolled out a system known as OccupEye, which tracked how long people spent at their desks.