Two early investors in ride-hailing company Uber have called on the company to change its “destructive culture” in the wake of sexual harassment and sexism allegations made by a former engineer who worked there. In a letter, Mitch and Freada Kapor said Uber’s success as a company could not “excuse a culture plagued by disrespect, exclusionary cliques, lack of diversity, and tolerance for bullying and harassment”, Reuters reported.

“Uber has had countless opportunities to do the right thing,” the Kapors wrote in the letter. “We feel we have hit a dead end in trying to influence the company quietly from the inside,” the letter said, according to Fortune.

The two said they were also disappointed that the cab aggregator had “selected a team of insiders” to investigate Susan Fowler’s claims. The two said the three-member team – former United States Attorney General Eric Holder, Uber human resources chief Liane Hornsey and board member Arianna Huffington – leading the inquiry into Fowler’s claims was “not set up to come up with an accurate analysis of the culture and a tough set of recommendations”.

Responding to the letter, Holder and his law firm partner Tammy Albarran said the inquiry would “leave no stone unturned” while investigating Uber. “We will be thorough, impartial and objective, and we are conducting this review with the highest degree of integrity and professionalism,” they said.

In a blog post, Fowler said her first manager had sent her messages saying that “he was looking for women to have sex with”. “When I reported the situation, I was told by both HR and upper management that even though this was clearly sexual harassment and he was propositioning me, it was this man’s first offence, and that they wouldn’t feel comfortable giving him anything other than a warning and a stern talking-to,” she had said. The former employee also detailed other incidents at the company, including sexist behaviour by HR department employees as well as team managers.

Her claims have once against brought the issue of discrimination by Silicon Valley companies and their users. In July 2016, house-sharing startup Airbnb hired Holder to investigate claims that homeowners were refusing to rent their residences to African-American guests.