Uber Technologies Inc. could be looking at paying £2.9 million, or about $3.9 million, to continue its operations in London –a  huge jump from the £2,826 the city’s transport regulator charged the ride-hailing giant in 2012.

Transport for London said the hike in licensing fees to all private car hire companies was imposed because of the explosion of such services in the capital and the growing difficulties in regulating the services. In a press release, TfL said that since 2013/14 the number of licensed drivers in the city had grown from 65,000 to 116,000, and the number of hired vehicles from 50,000 to 88,000.

“It is estimated that over the next five years enforcement costs alone will reach £30 million, up from a previous estimate of £4m,” said TfL. “The total projected cost for licensing, enforcement and compliance for the taxi and private hire trades over the next five years is £209m.”

Uber has been hit hard as it owns the lion’s share of the ride-hailing market in London. It’s thought that Uber has around 40,000 registered drivers in the city. TfL announced that the £2.9 million fee only would apply to operators with more than 10,001 vehicles. Companies with fleets numbering 1,001 – 10,000 would have to pay £700,000 to get the five-year license. For now, Uber is still waiting to see if indeed its license will be approved.

Uber’s dominance in London has not gone down well with some of London’s famed traditional taxi services, and its working conditions have come under scrutiny. Last week lawmakers and unions in the UK asked for the TfL not to approve a new license, stating that it was not a “fit and proper operator” and questions still needed to be asked about user safety and working conditions for drivers. More than 106,000 signatures were collected asking Uber to “respect workers’ rights or get out of London.”

Controversially, the TfL closed down an Uber competitor in London recently after it had promised to provide a much cheaper service and bigger profits for its drivers. Taxify, an Estonian-based ride-hailing start-up, had its license revoked after the TfL began an investigation into the company. In response, Taxify called the TfL “the most hostile regulatory body we have ever encountered.”

Image: Hernán Piñera via Flickr