Facebook fears that the confidential internal documents published by Parliament earlier this week may only be a fraction of what has been leaked.

Lawyers for the social media giant told a California judge on Friday that they still did not know what other material might now be in circulation and might soon be released.

The emails and memos, seized last month by MPs from an American app developer, Ted Kramer, and published on Wednesday, are part of a legal archive thought to include hundreds of thousands of documents.

"We literally don't know what information is out there," said Sonal Mehta, counsel for Facebook in court on Friday. "We have 250 pages that we know are public because they were published this week... but Mr Kramer can't tell us what else is out there or who else might have it.”

The documents were gathered as part of an ongoing lawsuit against Facebook by Mr Kramer's defunct app company, Six4Three, and had been sealed from the public by order of the judge.

Among them were emails showing that Facebook tried to strangle its competitors by cutting off their access to its data, as well as emails in which Facebook employees discussed how to read users' mobile phone logs without prompting a dialogue box asking for their consent.