Uber has been branded a "disgrace" by shadow chancellor John McDonnell after the firm lost its licence to operate in London.
Mr McDonnell was among a number of Labour figures to criticise the taxi app and praise the decision by Transport for London.
Speaking on Peston on Sunday, both the shadow chancellor and Unite union boss Len McCluskey echoed concerns raised about Uber.
And Labour leader Jeremy Corbyn concurred that the company had issues to address, but said Uber had an opportunity to "mend its ways".
TfL stripped Uber of its London licence, due to expire on September 30, over concerns about passenger safety and and vetting of its drivers.
Mr McDonnell showed no sympathy for the US firm and revealed that he had never travelled in an Uber cab.
The Hayes and Harlington MP told Peston: "The company is a disgrace. You have to abide by the law. If the company was outside the law, what could Transport for London do?
"I think the company is at fault here. Four months ago they were told to get their act together and they didn't."
Mr McCluskey also said he had never taken an Uber and would continue to use black cabs.
"I'm one of these people that believes that Uber is part of this horrible, race-to-the-bottom, culture that has developed in this country," he said.
Mr Corbyn said he was "not sure" if he had ever used an Uber.
He said: "What I think we need with Uber is decent pay and conditions for its staff."
The Labour leader added: "There is an issue about safety. Clearly the public as a whole want rapid access to taxis of all sorts, it should be regulated, the public should be protected."
He told BBC's Andrew Marr Show the dispute was "either going to go to court or they are going to mend their ways and make a new application and TfL will have to reconsider it".
More than 600,000 people have signed a petition calling for the decision not to grant a new licence to be reversed.
Uber says it intends to appeal the decision.