The Information Commissioner’s Office (ICO) has fined Facebook £500,000 for serious breaches of data protection law involving Cambridge Analytica that affected 87 million users, including nearly 1.1 million Britons.

In July, the ICO issued a Notice of Intent to fine Facebook as part of a wide ranging investigation into the use of data analytics for political purposes.

After considering representations from the company, the ICO has issued the fine to Facebook and confirmed the amount, which is the maximum allowable under the laws that applied at the time the incidents occurred.

The ICO’s investigation found that between 2007 and 2014, Facebook processed the personal information of users unfairly by allowing application developers access to their information without sufficiently clear and informed consent, and allowing access even if users had not downloaded a quiz app, but were simply “friends” with people who had.

Facebook also failed to keep the personal information secure because it did not make suitable checks on apps and developers using its platform. These failings meant one developer, Aleksandr Kogan and his company GSR, harvested the Facebook data of up to 87 million people worldwide, without their knowledge.

A subset of this data was later shared with other organisations, including SCL Group, the parent company of Cambridge Analytica which was involved in political campaigning in the US, the ICO said.

Even after the misuse of the data was discovered in December 2015, the ICO found that Facebook did not do enough to ensure those who continued to hold it had taken adequate and timely remedial action, including deletion. In the case of SCL Group, the ICO said Facebook did not suspend the company from its platform until 2018.

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

Elizabeth Denham, information commissioner, said: “Facebook failed to sufficiently protect the privacy of its users before, during and after the unlawful processing of this data. A company of its size and expertise should have known better and it should have done better.”

This fine was served under the Data Protection Act 1998. It was replaced in May by the new Data Protection Act 2018, alongside the EU’s General Data Protection Regulation (GDPR). These provide a range of new enforcement tools for the ICO, including maximum fines of £17m or 4% of global turnover.

“We considered these contraventions to be so serious we imposed the maximum penalty under the previous legislation. The fine would inevitably have been significantly higher under the GDPR. One of our main motivations for taking enforcement action is to drive meaningful change in how organisations handle people’s personal data,” said Denham.

“Our work is continuing. There are still bigger questions to be asked and broader conversations to be had about how technology and democracy interact and whether the legal, ethical and regulatory frameworks we have in place are adequate to protect the principles on which our society is based,” she said

A further update on the ICO investigation into data analytics for political purposes will be on 6 November, when the information commissioner will give evidence to the Department for Digital, Culture, Media and Sport (DCMS) Select Committee.

In July, the ICO published an interim progress update on its investigation and also published a partner report, Democracy disrupted? Personal information and political influence, looking at the broader policy issues identified during the investigation along with findings and the ICO’s recommendations for future action.