Britain’s data protection regulator has labelled Google as “irresponsible” for allowing advertisers to track customers’ digital “fingerprints”, amid fears even privacy-conscious users will find the online monitoring technique difficult to block.

The UK Information Commissioner’s Office (ICO) has warned the practice will undermine consumers’ control and choice over how their data is collected and used, and Google’s plan to allow its deployment departs from its “expectation of a privacy-driven internet”.

Fingerprinting involves gathering signals from a device’s software or hardware that together uniquely identify a user or device – a kind of supercharged version of cookies.

Fingerprinting is harder to spot and block and users cannot consent as easily as they do with the cookie windows that pop up often when browsing the internet, the data watchdog said.

This week, Google announced that from mid-February advertisers will be able to use it, citing the need for brands to better reach their desired audiences on smart TV, streaming services and internet-linked games consoles – a fast-growing advertising area known as connected TV (CTV). It also said there had been advances in technology that enhance customer privacy.

In 2019 Google had said: “Unlike cookies, users cannot clear their fingerprint, and therefore cannot control how their information is collected. We think this subverts user choice and is wrong.”

Stephen Almond, the ICO’s executive director for regulatory risk, said: “We think this change is irresponsible. Businesses do not have free rein to use fingerprinting as they please. Like all advertising technology, it must be lawfully and transparently deployed – and if it is not, the ICO will act.”

The ICO believes fingerprinting “is not a fair means of tracking users online because it is likely to reduce people’s choice and control over how their information is collected.”

It said the policy change meant fingerprinting could replace the functions of third-party cookies and that data protection law meant businesses must give users fair choice over whether to be tracked.

Google said it would hold further discussions with the ICO about the policy change.

A spokesperson for the company said: “Privacy-enhancing technologies offer new ways for our partners to succeed on emerging platforms like CTV without compromising on user privacy.

“We continue to give users choice whether to receive personalised ads, and will work across the industry to encourage responsible data use.”