LONDON — A British watchdog has slapped Facebook with a fine of 500,000 pounds ($644,000) — the maximum possible — for its behavior in the Cambridge Analytica scandal.

The Information Commissioner's Office's (ICO) investigation found that between 2007 to 2014, Facebook processed the personal information of users unfairly by giving app developers access to their information without informed consent.

The fine was the maximum allowed under the law at the time the breach occurred.

Had the scandal taken place after new E.U. data protection rules went into effect, the amount would have been far higher.

The British firm had worked closely with then-candidate Donald Trump’s campaign to target political ads to users during Trump's 2016 run for president — which ultimately led to an admission by Facebook that data from as many as 87 million users “may have been improperly shared with Cambridge Analytica.”

Facebook said it was reviewing the ICO's decision.

"While we respectfully disagree with some of their findings, we have said before that we should have done more to investigate claims about Cambridge Analytica and taken action in 2015," Facebook said in a statement. "We are grateful that the ICO has acknowledged our full cooperation throughout their investigation."

The ICO says it has found that the personal information of at least one million U.K. users was among the harvested data and consequently put at risk of further misuse.