A former security chief at Twitter has told US congress that the social media platform is plagued by weak cyber defences, privacy threats and an inability to control millions of fake accounts.

Peiter “Mudge” Zatko, a respected cyber security expert, appeared before the US senate judiciary committee to lay out his allegations.

As he began his sworn testimony, Mr Zatko said: “Twitter’s misleading the public, lawmakers” and regulators.

The platform is “over a decade behind the industry’s best standard,” he added. “This is a big deal for all of us.”

“It doesn’t matter who has keys if there are no locks.”

He was the head of security for the influential platform until he was sacked early this year.

Mr Zatko filed a whistleblower complaint in July with US congress, the justice department, the federal trade commission (FTC) and the securities and exchange commission.

Among his most serious accusations is that Twitter violated the terms of a 2011 FTC settlement by falsely claiming that it had put stronger measures in place to protect the security and privacy of its users.

Senators are clearly alarmed. Dick Durbin, an Illinois Democrat who heads the Judiciary Committee, said Mr Zatko has detailed flaws “that may pose a direct threat to Twitter’s hundreds of millions of users as well as to American democracy”.

He added: “Twitter is an immensely powerful platform and can’t afford gaping vulnerabilities.”

Mr Zatko’s claims could also affect Tesla billionaire Elon Musk’s attempt to back out of his 44 billion dollar deal to acquire the social platform.

Mr Musk claims that Twitter has long underreported spam bots on its platform and cites that as a reason to nix the deal he struck in April.

Many of Mr Zatko’s claims are uncorroborated and appear to have little documentary support.

Twitter has called Mr Zatko’s description of events “a false narrative … riddled with inconsistencies and inaccuracies” and lacking important context.

Mr Zatko also accuses the company of deception in its handling of automated “spam bots”, or fake accounts.

That allegation is at the core of Mr Musk’s attempt to back out of his deal to buy Twitter.

Mr Musk and Twitter are locked in a bitter legal battle, with Twitter having sued Mr Musk to force him to complete the deal.

The Delaware judge overseeing the case ruled last week that Mr Musk can include new evidence related to Mr Zatko’s allegations in the high-stakes trial, which is set to start October 17.

Senator Charles Grassley, the committee’s ranking Republican, said on Tuesday that Twitter CEO Parag Agrawal declined to testify at the hearing, citing the ongoing legal proceedings with Mr Musk.

But the hearing is “more important that Twitter’s civil litigation in Delaware,” Mr Grassley said.

Mr Zatko, 51, first gained prominence in the 1990s as an ethical hacker and later worked in senior positions at an elite US defence department research unit and at Google.

He joined Twitter in late 2020 at the urging of then-CEO Jack Dorsey.