Sadiq Khan has been dubbed a "charlatan" by Conservative rival Susan Hall.
She claimed the mayor has turned London into a "hotbed of crime and disorder".
Writing in an Op-Ed for the Daily Express, the Conservative Mayoral candidate for London said: "After yet another pathetic and evasive performance at Mayor's Question Time on Thursday, Khan once again provided a masterclass in mismanagement and an Olympic effort in dodging questions.
"It’s time for change. My New Year’s resolution is to rescue London from the clutches of our incompetent Mayor and build a safer, fairer, and happier city.
Sadiq Khan has been dubbed a "charlatan" by Conservative rival Susan Hall
PA
"I am determined to spend the next four months making my case to Londoners and exposing Sadiq Khan for who he is – a charlatan, and thanks to his unfair ULEZ expansion, the most accomplished highway robber since Dick Turpin.
"London was once a beacon of safety and prosperity.
"Under Sadiq Khan, who for nearly eight years has overseen the Met Police, it has descended into a hotbed of crime and disorder.
"Violent crime has skyrocketed, leaving ordinary Londoners constantly looking over their shoulders.
"The Met Police, once the pride of our city, has lost trust under Sadiq Khan's weak leadership, falling into special measures for the first time ever.
"Burglaries, robberies, and thefts are not investigated as much as they should be, and criminals are getting more brazen as a result."
But a source close to Sadiq Khan told GB News: "The Conservative candidate for Mayor couldn’t be more out of touch with our city and its values.
"She cheered Liz Truss’s mini-budget which sent Londoners’ mortgages and rents soaring.
"The Tory candidate would deliver more cuts to London’s public services, higher housing costs, and more inequality and division. The Tories have failed the country, we can’t let them fail London too.”
At Mayoral Questions this week, Hall suggested that Khan's Ulez was keeping Londoners apart at Christmas, claiming some Londoners have a choice between avoiding seeing relatives over Christmas or being slapped with a £12.50 charge.
Hall said: "It’s quite clear all you wanted for Christmas is Ulez and so that goes in despite 60 per cent of people saying that they definitely did not want it.
“Do you think it’s fair that people are going to have to either not see relatives over Christmas or pay £12.50 to you in order to come and see them if they haven’t got a car that complies?”
Khan said that while expanding Ulez was a "difficult decision", he said: "It’s the right thing to do".
The London Mayor added: "Just like drinking clean water is a right, breathing clean air is a right."
Khan claimed that 19 out of 20 cars are now Ulez compliant which means they do not pay the charge, but still "benefit from cleaner air".
Mayor's Questions also saw Hall criticised Khan for his record on violent crime.
She accused him of overseeing an almost 50 per cent rise in knife crime, something she described as being "disgraceful".
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But Khan insisted there had been a “significant” drop in the offences for those under 25.
The figure is down by 15 per cent.
The London Mayor added: “We will continue to make progress on this, not just by investing in police but by investing in services for young people.”