Social media platform Facebook unlawfully processed Dutch users' personal details without consent for advertising purposes for almost a decade, Amsterdam-based judges ruled on Wednesday.

The judgement by the Amsterdam District Court said Facebook Ireland -- custodians of Dutch users' personal details -- not only used the data for advertising, but also passed it to third parties without properly informing people or having legal grounds to do so.

"Facebook Ireland has broken the law when processing personal data of Dutch Facebook users in the period from April 1, 2010 to January 1, 2020," the judges said in a statement issued by the court.

It "processed personal data without a legal basis -- such as consent -- for this," the judges said.

Judges however turned down a third claim that the use of online "cookies", digital trackers used to target advertising, was unlawful on third party sites, as the responsibility to inform users was transferred to the relevant website operators  by Facebook Ireland.

The ruling comes after a 2019 class action lawsuit brought by the Dutch-based Data Privacy Foundation, an internet watchdog which says it fights for the rights of online users against companies "exploiting our personal details", backed by the country's Consumers Association.

The judges did not rule on claims in the case, but the Data Privacy Foundation's chairman Dick Bouma said it opened the door for consumers to receive "compensation for years of privacy violations by Facebook."

"It's now up to Facebook to provide this (compensation). We would like to discuss this with them," he told the NU.nl Dutch news website.

Facebook owner Meta in a statement to AFP said it was "pleased the court ruled in favour of Meta for multiple of these historic claims, some of which took place over a decade ago."

"We intend to appeal other aspects of this case," the statement said.

The Dutch court's finding followed a mega fine against Meta in early January, totalling 390 million ($410 million) euros, for breaching EU personal data laws on Facebook and Instagram.