State benefits agency UWV illegally gathered information from claimants more extensively than originally thought, broadcaster NOS has found.

An earlier investigation by the broadcaster and current affairs show Nieuwsuur had shown the agency had been recording IP addresses of benefit claimants who visited UWV and Werk.nl to see if they were abroad at the time, which would be in breach of the rules.

Everyone was targeted by the system even if there were no indications that they were involved in fraud, NOS said. The project was halted at the beginning of this year following recommendations by government lawyers, who said it breached privacy legislation.

It now turns out that instead of installing only “session” cookies, as it had claimed earlier, the agency had also placed cookies that monitored people’s location over time, even if they were not logged on, by linking visits the same device.

In this way, visits to the sites which could be months apart were collated, the agency admitted to the broadcaster.

The agency did not say if the gathered data had also been stored for longer periods, saying only that “some cookies last longer than others depending on what they were used for.”

Policy advisor Nadia Benaissa of civil rights organisation Bits of Freedom called the doings of the UWV “the wild West”. “The fact they used these cookies over such a long time shows a complete disregard for privacy rules,” she told the broadcaster.

Lawyer Anton Ekker, who successfully prosecuted the state for the use of algorithms to detect fraud said the UWV was involved in “secret surveillance”. “The longer you watch people, the more serious the breach of privacy, so this is even worse than we thought.”

Privacy watchdog Autoriteit Persoonsgegevens (AP) told the broadcaster it has scheduled a meeting with the UWV.