Hundreds of black cabs blocked Whitehall, Westminster, in a protest against private hire app Uber on Thursday (7 March).

But unfortunately for the United Cabbies Group, LTDA and RMT Union, who organised the demonstration, MPs were not in the House of Commons because of the parliamentary recess.

More from IBTimes UK

The groups instead handed a letter to Number 10 demanding a parliamentary inquiry into taxi and private hire regulations as well as the relationship between David Cameron and Uber.

Jon Cruddas, the Labour MP for Dagenham and Rainham, has also raised concerns in a letter to Theresa May. "The revelations published last week in the Mail, The Sun, and the Financial Times suggest that Number 10 under David Cameron acted as a full signed up lobbyist of Uber at the expense of a fair and effective regulatory framework for the industry," he said.

"I am certainly not opposed to disruptive technology and competition, but Uber's conduct in London and other cities around the world has raised serious issues in terms of fair competition, workers' rights, passenger safety and fair corporate taxation."

More than 200,000 people signed a petition in 2015 opposing Transport for London proposals to, among other things, make Uber customers wait five minutes between booking their car and starting their journey.

The plan was dropped under then Conservative Mayor of London Boris Johnson, who was reportedly contacted by Cameron and former Chancellor George Osborne over the issue via text.

An Uber spokesperson said: "Londoners will struggle to understand why black cab drivers have once again brought the capital's streets to a standstill. Just two days ago the Mayor exempted diesel cabs from his new air pollution charge which everyone else - even ambulances - will have to pay.

"Meanwhile Transport for London is pursuing new measures which its own estimates show will put more than 33,000 private hire drivers out of business. We'll be doing our best to help keep London moving this afternoon."

Uber David Cameron