London mayor Sadiq Khan is to spend £50m on a Green New Deal for London as part of a pledge to make the UK capital carbon neutral by 2030.

The mayor, who faces the electorate in May, said the announcement highlights his commitment to tackling the climate crisis and improving London’s dangerous levels of air pollution.

“I’m unapologetic at how ambitious my plans are for a Green New Deal for London because we can’t afford not to be ambitious when it comes to saving our planet,” Khan told the Guardian.

In May’s election he faces a challenge from Tory candidate Shaun Bailey, former Conservative cabinet member Rory Stewart – who is standing as an independent – as well as candidates from the Green party, the Liberal Democrats and the Women’s Equality party.

But announcing the new fund, which officials said comes from higher council tax and business rates, Khan insisted May’s election was a “two horse race” between him and Bailey – and made a direct pitch for green votes.

“The Tory candidate and I are the only candidates who can win this election,” he said. “Which is why I’m making a direct appeal today to Londoners who have previously supported the Green party to lend me their vote on 7 May so that I can stand up for our shared values and take action on climate change.”

The mayor has introduced an ultra-low emissions zone (Ulez) in central London which is due to expand to the north and south circulars in 2021. However, other cities – including Manchester and Birmingham – have announced ambitious plans to improve air quality and encourage cycling, and Khan has been criticised for not moving quickly enough.

But the mayor insisted he was determined to make London a leading green city.

“These issues are personal to me. I don’t want my children to grow up in a world where our very way of life is threatened by the climate crisis. And as someone who suffers from adult onset asthma, I understand the price we pay for failing to clean up our toxic air.”

Green groups welcomed the new fund but said Khan must go further if he is re-elected in May.

Jenny Bates, campaigner at Friends of the Earth, said the climate and nature crisis was the biggest threat the world faced, adding air pollution in London was “a health scandal”.

“While the mayor has made good strides on these issues, much more needs to be done to cut emissions from all sectors. This means expanding the Ulez to the whole of London, not just to the north and south circular roads. We also need more infrastructure to make cycling and walking safer and easier for everyone, along with clear action to cut traffic levels which a London-wide pay-as-you-go driving system would help deliver.”

Bates also criticised the mayor for approving the four-lane Silvertown road tunnel in east London which she said would make “already illegally bad air breathed in some areas even worse”.

“There is no place for large scale road-building in London given the climate and air pollution imperatives, nor for any airport expansion at City airport or Heathrow.”

Doug Parr, policy director at Greenpeace, said it was right that all candidates for London mayor prioritised the climate emergency.

“We will see what all parties have to offer but this is a helpful pledge to increase the priority that climate protection receives in a city of global significance such as London,” he added.

City Hall officials said the new fund had not been allocated to specific programmes yet but proposals being considered included making homes energy efficient, creating new green spaces and speeding up the installation of solar panels in the capital.