Taxify, the rival to ride-sharing company Uber, has had its services suspended by London's transport authority over alleged licensing issues.
Transport for London said Taxify did not have a valid license to offer services and ordered the company to halt activity after just three days of operations.
"TfL has instructed Taxify to stop accepting bookings and it has done so," a TfL spokesperson said on Friday.
Estonia-based Taxify, which recently partnered with China's Didi Chuxing, launched its service in London on Sept 5.
Chief Executive Officer Markus Villig said the company will appeal the decision and plans to resume operations as soon as possible.
Taxify is "fully compliant with UK law", Villig said.
Taxify launched in London promising to challenge Uber- the only major mobile platform for private hire cabs in the city－with lower prices and better driver pay. It says it has 3,000 drivers in London.
Villig, who said 30,000 UK users downloaded the app last week, labelled TfL "the most hostile regulatory body we have ever encountered".
"TfL has done everything in their power to keep the current private hire monopoly in place," he said.
Villig said that while Taxify had not been granted an operating license by TfL, the company acquired licensed London operator City Drive Services in August.
He said that Taxify is a technology company that provides City Drive Services with the software to receive and manage bookings.
"More than four months ago we applied for a private hire operator license," Villig said."Over this time, we contacted TfL more than 20 times, without a single reply on the clear status of the application."
He added: "After failing to get any response from TfL, we started contacting existing licensed private hire operators to offer our technology platform to them. We acquired one of these licensed operators, City Drive Services, and granted them a license to use the technology, which is fully compliant with UK law."
Villig said TfL has revoked City Drive Services' license.
He also claimed that TfL launched a what he called"secretive investigation" last week in which officials booked rides on the Taxify app and threatened drivers with the loss of their license.
London Mayor Sadiq Khan has confirmed that Tfl had conducted an inquiry into Taxify.
"Following an investigation, it was right that TfL took immediate action to instruct Taxify to cease operating,'' Khan said in a statement. "I will continue to do everything I can within my powers to drive up standards across the taxi and private hire market, and ensure Londoners can get safely around our city."
Villig said City Drive Services will appeal the revoking of its license and Taxify hopes to resume service in London.
