Sadiq Khan has unveiled plans to crack down on illegal taxis and minicabs - but transport union RMT has complained the drive will fail to look at smartphone services like Uber.
Transport for London (TfL) will hire an additional 250 hi-vis wearing compliance officers by September 2017, quadrupling the number available to tackle illegal cabs at sites across London including Kings Cross, Heathrow and the West End.
Khan said the effort will represent the first step in a programme to improve standards across London's taxi industry.
Reforms will include requiring cabs to accept card payment from 3 October, as well as efforts to improve the environmental friendliness of London taxis.
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However, the boss of transport union RMT has said the plans fall short, with neither TfL nor City Hall willing to look at the role of "e-hailing" smartphone taxi services like Uber.
"This practice circumvents the current regulation regime which is there to protect the travelling public. Neither TfL or the Mayor appear to have the will to tackle this blatant flouting of the regulations by the likes of Uber," RMT general secretary Mick Cash said.
"In addition, proposals laid out in a recent consultation review of Private Hire regulations are to be revisited under Mayor Khan's administration. The union is deeply concerned that yet again they fail to regulate the virtual plying for hire of private hire vehicles which is now endemic on our streets."
Uber London general manager Tom Elvidge responded: "We welcome this move to tackle unlicensed cars and illegal activity in London. It's important that people only use a properly booked car from a licensed private hire operator.
"Our technology means it's convenient, safe and affordable to book a licensed car when you need one and we give Londoners the name, registration number, contact details, photo and rating of their licensed driver."