Facebook is co-operating with Britain's Information Commissioner's Office (ICO) as it examines how 30 organisations have used personal data, but the ICO said on Thursday it was too early to say whether the social media giant had done enough.

On Wednesday, Facebook said the personal information of up to 87 million users, mostly in the United States, may have been improperly shared with political consultancy Cambridge Analytica, more than previous estimates.

The ICO said it was looking at how data was collected from a third party app on Facebook and shared with Cambridge Analytica, as well as a broader investigation into how social media platforms have been used in political campaigning.

"Facebook has been co-operating with us and, while I am pleased with the changes they are making, it is too early to say whether they are sufficient under the law," the information commissioner, Elizabeth Denham, said in a statement.

"As part of my investigation into the use of personal data and analytics by political campaigns, parties, social media companies and other commercial actors, the ICO is investigating 30 organisations, including Facebook."

Britain's digital and media minister Matt Hancock said he would meet Facebook next week to discuss the scandal. Facebook shares are down over 10 percent since it first disclosed the leak.

"I expect Facebook to explain why they put the data of over a million of our citizens at risk," Hancock said in a tweet.

"This is completely unacceptable, and they must demonstrate this won't happen again."