The Facebook whistleblower whose revelations have tipped the social media giant into crisis has launched a stinging new criticism of Mark Zuckerberg, saying he has not shown any readiness to protect the public from the harm his company is causing.

Frances Haugen told the Observer that Facebook’s founder and chief executive had not displayed a desire to run the company in a way that shields the public from the consequences of harmful content.

Her intervention came as pressure mounted on the near-$1tn (GBP730bn) business following a fresh wave of revelations based on documents leaked by Haugen, a former Facebook employee. The New York Times reported that workers had repeatedly warned that Facebook was being flooded with false claims about the 2020 presidential election result being fraudulent and believed the company should have done more to tackle it.

Haugen, who appears before MPs and peers in Westminster on Monday, said Zuckerberg, who controls the business via a majority of its voting shares, has not shown any willingness to protect the public.

“Right now, Mark is unaccountable. He has all the control. He has no oversight, and he has not demonstrated that he is willing to govern the company at the level that is necessary for public safety.”

She added that giving all shareholders an equal say in the running of the company would result in changes at the top. “I believe in shareholder rights and the shareholders, or shareholders minus Mark, have been asking for years for one share one vote. And the reason for that is, I am pretty sure the shareholders would choose other leadership if they had an option.”

Haugen, who quit as a Facebook product manager in May, said she had leaked tens of thousand of documents to the Wall Street Journal and to Congress because she had realised that the company would not change otherwise.

She said: “There are great companies that have done major cultural changes. Apple did a major cultural change; Microsoft did a major cultural change. Facebook can change too. They just have to get the will.”

This weekend, a consortium of US news organisations released a fresh wave of stories based on the Haugen documents. The New York Times reported that internal research showed how, at one point after the US presidential election last year, 10% of all US views of political material on Facebook – a very high proportion for Facebook – were of posts falsely alleging that Joe Biden’s victory was fraudulent. One internal review criticised attempts to tackle Stop the Steal groups spreading claims on the platform that the election was rigged. “Enforcement was piecemeal,” said the research.

The revelations have reignited concerns about Facebook’s role in the 6 January riots, in which a mob seeking to overturn the election result stormed the Capitol in Washington. The New York Times added that some of the reporting for the story was based on documents not released by Haugen.

A Facebook spokesperson said: “At the heart of these stories is a premise which is false. Yes, we’re a business and we make profit, but the idea that we do so at the expense of people’s safety or wellbeing misunderstands where our commercial interests lie. The truth is we’ve invested $13bn and have over 40,000 people to do one job: keep people safe on Facebook.”

Facebook’s vice-president of integrity, Guy Rosen, said the company had put in place multiple measures to protect the public during and after the election and that “responsibility for the [6 January] insurrection lies with those who broke the law during the attack and those who incited them”.

It was also reported on Friday that a new Facebook whistleblower had come forward and, like Haugen, had filed a complaint to the Securities and Exchange Commission, the US financial regulator, alleging that the company declined to enforce safety rules for fear of angering Donald Trump or impacting Facebook’s growth.

Haugen will testify in person on Monday to the joint committee scrutinising the draft online safety bill, which would impose a duty of care on social media companies to protect users from harmful content, and allow the communications regulator, Ofcom, to fine those who breach this. The maximum fine is 10% of global turnover, so in the case of Facebook, this could run into billions of pounds. Facebook, whose services also include Instagram and WhatsApp, has 2.8 billion daily users and generated an income last year of $86bn.

As well as issuing detailed rebuttals of Haugen’s revelations, Facebook is reportedly planning a major change that would attempt to put some distance between the company and its main platform. Zuckerberg could announce a rebranding of Facebook’s corporate identity on Thursday, according to a report that said the company is keen to emphasise its future as a player in the “metaverse”, a digital world in which people interact and lead their social and professional lives virtually.

Haugen said Facebook must be compelled by all regulators to be more transparent with the information at its disposal internally, as detailed in her document leaks. She said one key reform would be to set up a formal structure whereby regulators could demand reports from Facebook on any problem that they identify.

“Let’s imagine there was a brand of car that was having five times as many car accidents as other cars. We wouldn’t accept that car company saying, ‘this is really hard, we are trying our best, we are sorry, we are trying to do better in the future’. We would never accept that as an answer and we are hearing that from Facebook all the time. There needs to be an avenue where we can escalate a concern and they actually have to give us a response.”