Mark Zuckerberg “has unilateral control over 3 billion people” due to his unassailable position at the top of Facebook, the whistleblower Frances Haugen told MPs as she called for urgent external regulation to rein in the tech company’s management and reduce harm to society.

Haugen, a former Facebook employee who released tens of thousands of damaging documents about its inner workings, travelled to London from the US for a parliamentary hearing and gave qualified backing to UK government proposals to regulate social media platforms and make them take some responsibility for content on their sites.

The company’s internal culture prioritised profitability over its impact on the wider world, said Haugen, and “there is no will at the top to make sure these systems are run in an adequately safe way”. She added: “Until we bring in a counterweight these things will be operated for the shareholder’s interest and not the public interest.”

She warned that Instagram, which is owned by Facebook and used by millions of children worldwide, may never be safe for pre-teens.