Meta adopted a “don’t ask, don’t tell” approach to child safety on its social media platforms, according to a whistleblower who testified against the company during a landmark trial on Tuesday and Wednesday.

Arturo Béjar, a former Meta safety engineer, told jurors that the company knew its products were exposing children to harmful content, including recommendations featuring sexual predators as well as violent and graphic material. He said he repeatedly raised these concerns with Facebook and Instagram executives, but little was done to address them.

Béjar said his responsibilities often included briefing Meta CEO Mark Zuckerberg on product-related issues and estimated that he spoke with the executive at least 100 times.

He also cited a 2021 email he sent to Zuckerberg warning about persistent reports of harmful content and the negative impact of Facebook and Instagram on teenagers’ wellbeing.

Béjar said he sent the email after Zuckerberg publicly stated that Meta did not prioritise profits over user safety.

“I felt that he created a false and misleading impression of Facebook’s commitment to young people,” Béjar testified.

US states have accused Meta of concealing research into social media addiction among teenagers, as a former company safety engineer delivered key testimony in a landmark trial against the technology giant.

Arturo Béjar, a former Meta safety engineer, said he sent reports about harmful experiences involving teenagers directly to Meta CEO Mark Zuckerberg because of the executive’s influence over the company.

“In my experience, when Mark makes something a priority, mountains move,” Béjar told the court.

His testimony forms part of a case in which US states are seeking to hold Meta accountable for allegedly misleading the public about the risks its platforms pose to children and teenagers.

The states have also accused the company of withholding or downplaying internal research into the potentially addictive effects of its social media platforms on young users.

“Did he ever respond to you?” the attorney representing the government asked.

“No,” Béjar replied. “I didn’t hear back from him.”

Béjar was the first witness to testify in the federal trial, which began with opening statements on Tuesday. The case was filed against Meta by attorneys general from 29 US states, who allege that the social media company deliberately designed addictive products to attract young users, exposing them to harm.

The state officials also accuse the trillion-dollar technology company of routinely collecting personal data from children under 13 without parental consent, allegedly in violation of federal and state laws.

The trial is expected to examine Meta’s internal practices and its handling of research and warnings about the potential effects of its platforms on children and teenagers.

“I heard from many of you at jury selection that the health and wellbeing of kids is a shared responsibility,” said Megan O’Neill, deputy attorney general for California, in her opening statements. “Meta didn’t do its share.”

Other witnesses expected to testify include Meta CEO Mark Zuckerberg and Instagram head Adam Mosseri, as well as other company executives and experts in children’s mental health and addiction.

The trial has also featured extensive internal Meta documents and emails that have been released as evidence.

The proceedings are taking place in Oakland, California, and are expected to continue for at least six weeks.