Thousands of London's black-cab drivers have brought Whitehall to a standstill in protest over safety fears and regulations. Unite and United Cabbies Group made the move after Transport for London (TfL) dropped plans for private-hire vehicle operators to wait at least five minutes between pick-ups.

The draft rule was among a number of ideas floated by TfL in a consultation which closed in December 2015. But the body's decision not to adopt some of the suggested regulations has sparked a new "fairness" row as drivers using applications such as Uber have fewer rules to abide by.

Tom Elvidge, general manager of Uber in London, described the proposed rules as "bureaucratic". He added: "We believe black cabs and services like Uber can co-exist in the capital. That's why earlier this week we announced that black-cab drivers can use our app to get extra custom with zero service fee paid to Uber for a year. By making the most of new technology we can all improve services for passengers and keep London moving."

Meanwhile, TfL defended its decision and claimed the public gave the organisation a "very clear indication" they did not want the regulation introduced in the capital.

Garrett Emmerson, TfL's chief operating officer for surface transport, said: "Londoners gave us a very clear indication of how they wanted us to shape the regulation to deliver improved safety and customer service, and we are now progressing a wide range of measures to ensure both the taxi and private-hire trades can thrive in the future."

The dispute also has an extra layer of complexity since it comes amid the contest to be the next mayor of London. Zac Goldsmith MP, the Conservative candidate for City Hall, has promised to "stand up" for black cab drivers if elected in May.

"This is an important first step in levelling the playing field and delivering greater choice and convenience for Londoners. The election in May is about who will keep their promises, and this is my pledge to protect our much-loved cabs and help them survive long into the future," he said.

His Labour rival Sadiq Khan, meanwhile, has pledged to limit the number of private-hire vehicles operating in London, telling The Memo there are far too many of them. "Right now there is no cap or limit," he said. "Every year it's gone up by 12,000 over the past three years and we've got to do something about it."