Transport for London (TfL) has asked British tax officials at Her Majesty's Revenue & Customs (HMRC) to investigate San Francisco car-sharing service Uber.
The move by the minicab regulator comes after Labour MP Margaret Hodge said that Uber was "opting out of the UK tax regime".
Uber's operating arm, Uber BV, is based in the Netherlands, meaning the company does not pay tax on profits it makes through its UK business
Mayor of London and TfL chair Boris Johnson said TfL does not have the power to enforce where a company pays tax.
"TfL has raised this issue to the appropriate body, the HMRC, for them to consider," he wrote in a letter to Hodge, which she said she was "pleased" to receive via Twitter.
"I hope that HMRC will carry out a rigorous and thorough investigation to ensure that Uber is paying an appropriate level of tax in the UK, rather than constructing artificial structures to get out of paying its fair share," she told the BBC.
An Uber spokesman told the BBC that it complied with all applicable tax laws and "pays taxes in all jurisdictions, such as corporate income tax, payroll tax, sales and use tax and VAT".
Uber, founded in 2009, describes itself as a "pick-up" service that connects passengers with vetted private drivers. The company's app, which has been backed by Google, Goldman Sachs and others, permits customers to order taxis through their smartphone, see who their driver will be, and track the arrival of their car. It is often significantly cheaper and faster than rival companies.
The Uber platform has proved popular in several countries, much to the annoyance of the licensed taxi businesses already operating there.
The taxi service, recently valued at $18.2 billion (£10.6 billion), was targeted by thousands of black cab drivers in June who took to the streets in protest, claiming Uber was operating unlawfully by using a smartphone app to work out fares when its illegal for private vehicles to be fitted with taximeters.
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