The GMB union in the UK has called for HM Revenue & Customs, the British agency charged with the collection of taxes, to investigate human cloud firm Uber for wage compliance.

“We have formally requested today that HMRC investigate the dark maze of tax avoidance at Uber,” said GMB Legal Director Maria Ludkin. “The recent judgement shows that Uber drivers are workers, employed by Uber. The company can no longer try to pass the buck of tax responsibility to drivers by pretending they are self-employed.”

GMB’s move follows a decision by a tribunal in London that two Uber drivers should be classified as employees instead of independent contractor. It’s a decision that Uber is fighting.

“HMRC should recover employers national insurance contributions and employee PAYE tax and national insurance contributions from Uber for the drivers,” Ludkin said in the statement. “As GMB demonstrated in the Tribunal, one driver’s average pay for driving hours was £5.68 and zero for time waiting for work.”

PAYE tax refers to “pay-as-you-earn tax” and is a withholding tax on income payments to employees.

In her statement, Ludkin also said Uber will likely have to raise fares to comply with employment laws, and that move would make it “less predatory for the rest of the industry.”

Separately, Labour MP Jack Dromey called on Uber to change its business practices, Business Insider reported. Dromey is also shadow minister for labour.