Uber is back in the news and, as seems to happen so often, not for good reasons. Susan Fowler is a former web engineer at Uber who left the cab-hailing app in December.

She wrote on her website a lengthy blog post detailing allegations of sexual harassment and workplace sexism, and the shoddy response to her complaints by Uber's HR department.

"When I joined Uber, the organisation I was part of was over 25% women," Fowler wrote. "By the time I was trying to transfer to another eng organisation, this number had dropped down to less than 6%. Women were transferring out of the organisation, and those who couldn't transfer were quitting or preparing to quit.

"There were two major reasons for this: there was the organisational chaos, and there was also the sexism within the organisation.

"When I asked our director at an org all-hands about what was being done about the dwindling numbers of women in the org compared to the rest of the company, his reply was, in a nutshell, that the women of Uber just needed to step up and be better engineers."

The Uber CEO Travis Kalanick described Fowler's experiences as "abhorrent [and] against everything we believe in. Anyone who behaves this way or thinks this is OK will be fired." He said he had instructed Liane Hornsey, Uber's chief human resources officer, to investigate, though some Twitter users questioned the independence of such an inquiry.

Yet again, Uber, which has an estimated value of around $70bn (£56bn), is putting out a reputational fire. Here are some of the other scandals and problems to have gripped Uber in its short eight-year history.

Sexual assaults and harassment by Uber drivers

There are lots of anecdotal reports from women passengers of sexual assault and harassment by their Uber drivers. Uber claimed in March 2016 that it was aware of 175 rides where sexual assault allegations were made across all of its journeys between December 2012 and August 2015, five of which were rapes. This equates to 1 in every 3.3 million trips, said the company.

It was responding to a report by BuzzFeed, which was leaked screenshots of the customer support system, where "tickets" are logged for each case and suggested the problem could be much bigger. "In one screenshot, a search query for 'sexual assault' returns 6,160 Uber customer support tickets," said the BuzzFeed story. "Other variations of the terms yield similarly high returns: A search for 'assaulted' shows 3,524 tickets, while 'sexually assaulted' returns 382 results."

A freedom of information request in 2016 by The Sun to the Metropolitan Police found there had been 32 allegations of sexual assault made against Uber drivers in 12 months. In all, there were 154 allegations made against taxi drivers, including minicabs, chauffeurs and rickshaw riders.

Uber says it runs criminal background checks on its drivers and does not tolerate misconduct. "Any behaviour involving violence, sexual misconduct, harassment, discrimination, or illegal activity while using Uber can result in the immediate loss of access to your account," Uber warns drivers in its policy.

In November 2016, Uber settled a lawsuit brought by two women who said the company was responsible for their sexual assaults by Uber drivers, who were contractors rather than employees. The year before, Uber settled in India with a woman who had accused an Uber driving of raping her during a ride in New Delhi.

Uber drivers are accused of using underhand tactics to hurt rival apps

In California in 2014, Uber employees were accused of ordering several thousand fake rides on the rival app Lyft, therefore reducing driver availability, and the company is the subject of an ongoing lawsuit by Lyft drivers over the issue. It faced similar accusations in New York from the rival app Gett. Uber said at the time it would "make sure [our local teams] tone down their sales tactics".

Low pay for Uber drivers

Uber, which says it is a platform for contractors, faces calls the world over from its drivers for much better working conditions. In San Francisco, there is a lawsuit ongoing brought by drivers who argue they should be treated like employees.

Many drivers claim they earn just a handful of dollars an hour, sometimes less than the minimum wage, after various deductions from the fare, some of which go to Uber, the rest on the costs of running the car. Drivers say Uber's aggressive pricing strategy – it often slashes fares to compete –leave them much worse off and having to work very long hours. It's a similar story in India.

In London, Uber was taken to employment tribunal by two drivers who argued they should count as workers, not contractors, and therefore be entitled to certain employment rights, including being paid at least the minimum wage, holiday pay, and sick pay. The judge ruled in their favour in a landmark decision which will impact the so-called "gig economy".

Accusations of scabbing during the Muslim ban protests

There was a huge #DeleteUber backlash against the app when it emerged the company suspended its "surge pricing" – effectively a fare cut – in New York as the city's yellow taxi drivers stopped working in protest against Donald Trump's controversial travel ban on seven Muslim-majority countries.

Uber's fares increase when demand is high and fewer cars are available, so the firm was capitalising on the taxi drivers' protest. To quell the backlash, Uber CEO Travis Kalanick created a $3m legal fund to support its drivers impacted by the travel ban.

Spying on journalists

Uber has had a troubled relationship with journalists. Emil Michael, senior vice president of business at Uber, was recorded by BuzzFeed suggesting the company hire researchers to dig up dirt on its critics in the media by looking into their personal lives and families.

Michael later said the remarks were wrong, that they do not reflect his real views, and they were "borne out of frustration during an informal debate over what I feel is sensationalistic media coverage of the company I am proud to work for".

It later emerged that Josh Mohrer, the general manager of Uber's New York office, had accessed the travel data of BuzzFeed reporter Johana Bhuiyan without her permission, breaching Uber's privacy policy. He had also emailed her her own Uber travel logs when she had asked questions about Lyft. He was disciplined.