The London Assembly has unanimously voted to ask Sadiq Khan not to renew Uber's licence unless the company improves working practices.
The Mayor of London recently renewed the digital cab service's private hire licence from May 2017 to September 2017, despite concerns over driver welfare, reports of sexual assault and others.
The Assembly also expressed concern over the alleged corruption allegations against Uber over its close ties to former Prime Minister David Cameron and his Chancellor George Osborne reported in the Daily Mail in March .
The motion, proposed by UKIP Assembly Member David Kurten, was passed on Thursday (July 6) and included some strong wording.
"This Assembly is appalled at some of the work practices of Uber and is extremely concerned about the effects of these practices on other PHV operators, black cabs and even their own drivers," it read.
The Assembly called on the Mayor, as Chairman of TfL, not to renew the firm's licence beyond September unless working practices are altered.
David Kurten AM, who proposed the original motion said: “The Mayor pledged in his election campaign to revoke Uber’s licence if there was just case of poor practice as he would not compromise on Londoners’ safety.
"One year on from his election he has renewed Uber’s operating licence despite grave concerns about Uber’s working practices, driver safety, increased allegations of sexual assaults by Uber drivers, tax avoidance and the potential quagmire of alleged corruption between Uber’s previous bosses and members of David Cameron’s administration.
"I believe there are now so many problems caused by Uber’s practices that they do not deserve any more chances.
"It is time to pull the plug on Uber in London - unless it does something dramatic about its working practices.”
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Navin Shah AM, who proposed the amended motion, said: "To say Uber’s working practices leave a lot to be desired is an understatement.
"We know this isn't just taking its toll on Uber drivers but on the wider private hire industry and on cabbies too."
An Uber spokesperson said: “Millions of Londoners rely on Uber to get a reliable ride at the touch of a button and thousands of licensed drivers make money through our app.