Facebook boss Mark Zuckerberg will not answer questions from British lawmakers over how millions of users' data got into the hands of political consultancy Cambridge Analytica as the company faces further pressure on both sides of the Atlantic.

Zuckerberg will instead send his chief technology officer Mike Schroepfer or chief product officer Chris Cox to appear before parliament's Digital, Culture, Media and Sport committee.

In response, its chairman said on Tuesday that lawmakers still wanted to speak to Zuckerberg and would see whether they could set up a session in person or via video link.

Zuckerberg apologised last week for the mistakes Facebook had made and promised tougher steps to restrict developers' access to such information, which saw the company's share price fall and prompt new questions from politicians and regulators.

In response to a request by British lawmakers to appear before them, the firm's head of UK Public Policy told lawmakers that Schroepfer or Cox were better placed to answer questions.

"Facebook fully recognised the level of public and Parliamentary interest in these issues and supports your belief that these issues must be addressed at the most senior levels of the company by those in an authoritative position," wrote Rebecca Stimson.

"As such Mr Zuckerberg has personally asked one of his deputies to make themselves available to give evidence in person to the Committee."