Sadiq Khan has pledged not to extend the scope of London’s ultra-low emission zone (Ulez) scheme if he returns to the role after May’s election. In a letter to the Transport for London commissioner, Andy Lord, the capital’s mayor wrote that he had “categorically” ruled out the introduction of a pay-per-mile scheme as well as any tightening of Ulez emissions standards. He wrote: “There is clearly still more to do to tackle air pollution, and I’m determined to continue leading from the front in London. “But my commitment to Londoners is this will not include a new pay-per-mile road user charging scheme or amending the standards for the Ulez scheme. “The introduction and expansion of the Ulez has been necessary and effective. But now it’s in place and working, I will ensure the goalposts are not moved for drivers.” Khan adds in the letter that he would focus on other measures to tackle air pollution, including improving walking and cycling routes, making buildings more energy efficient and expanding the network of electric vehicle charging stations. Susan Hall, the Conservative mayoral candidate, said: “Promises are worthless from the man who has been dishonest with Londoners about his plans to tax drivers. “Sadiq Khan said he wouldn’t expand Ulez at the last election, then went ahead and did the opposite. He has spent £150m building the technology for pay per mile, and now wants us to believe he won’t use it. “Sadiq Khan is taking Londoners for fools and he just won’t listen. That’s why we need to vote for change on 2 May.” A spokesperson for the mayor said: “Sadiq has been clear that he has ruled out the introduction of a pay-per-mile road user charging scheme but the Tories are clearly trying to mislead Londoners by repeatedly saying this is not the case. “The mayor has now put in writing to the TfL commissioner his clear pledge to London: no pay-per-mile scheme will be introduced while he is mayor.” The Liberal Democrat candidate, Rob Blackie, said: “The Ulez could have been so much more successful if the mayor hadn’t rushed the 2023 extension, giving people in outer London just a few months to adapt. “If we’re going to crack climate change we need to bring people with us. It’s crucial that the mayor focuses on fixing the problems that still persist, especially for tradespeople who need vans for work.” The Green party has been approached for comment.