Mr Khan’s predcessor, Boris Johnson, had promised taxpayers would step in and cover maintenance costs for the bridge’s entire 120 year lifespan should the Trust behind the project be unable to cover its bills.
The commitment was criticised by London Assembly members and campaign groups opposed to the bridge on the grounds that it would considerably increase risk to the taxpayer.
Mr Johnson’s guarantee, which has yet to be signed, was a requirement of the Port of London Authority and a condition of Lambeth and Westminster councils’ respective planning approvals which state it must be signed and in place before construction can commence.
On Friday Mr Khan said he would not sign the pledges and that the Trust would have to try and amend its planning conditions to allow the project to proceed without further taxpayer support.
Mayor Khan said: “Under the previous Mayor, a considerable amount of London taxpayers’ money has already been spent on the Garden Bridge. I have always been clear that not a penny more of taxpayers’ money should be allocated to the project.”
“With planning permission due to expire this year, many outstanding issues remain, including spiralling construction costs and doubts around funding the maintenance of the bridge.
“The funding gap is now at over £70million and it appears unlikely that the Trust will succeed in raising the private funds required for the project.
“I am simply not prepared to risk a situation where the taxpayer has to step in and contribute significant additional amounts to ensure the project is completed.”
The Mayor’s office says he made his decision following study of Dame Margaret Hodge’s recently published review into the project.
Welcoming the Mayor’s decision, Labour London Assembly Member Tom Copley AM, said: “It is excellent news that the Mayor will not be signing the Garden Bridge maintenance guarantee.
“How this project got as far as it has done is beyond belief.
“From the flawed procurement process, to allegations of conflict of interest, to extremely poor value for money, the Garden Bridge project has been disastrous every step of the way.
“Millions of pounds of public money has been wasted on what is essentially Boris Johnson’s vanity project, despite a range of objections from a number of London Assembly Members.
“I am absolutely delighted that Mayor Khan is putting an end to this piece of Johnsonian indulgence and placing the interests of Londoners and taxpayers first.”
Liberal Democrat AM Caroline Pidgeon, who called on the Mayor to axe the bridge after he came to office last May, commented: “The Mayor has taken a year to make this decision and while he has been dithering more money has been wasted.
“Yet while it is regrettable that Sadiq Khan has taken so long to make a decision he has finally done the right thing following Dame Margaret Hodge’s damning report.
“it is quite clear this vanity project of Boris Johnson’s would end up as a bottomless pit for the public purse.
“It is now dead in the water and will be held up for many years as a case study on wasting public money and poor decision making at both government and Mayoral level.”