Mayor of London Sadiq Khan has given his clearest indication yet that he will not allow construction work on the Garden Bridge to begin if there is a chance of public money being required to meet maintenance and operational costs.
Under the terms of planning permissions granted by Westminster and Lambeth councils, construction work on the controversial Thomas Heatherwick-designed footbridge between the South Bank and Temple cannot begin unless arrangements to underwrite the bridge's annual operating and maintenance costs – estimated at around £3 million – have been made.
Former Mayor of London Boris Johnson made provision for that guarantee to be provided by the London taxpayer, but binding agreements have yet to be signed.
Answering a question tabled by Liberal Democrat London Assembly member Caroline Pidgeon, Sadiq Khan has indicated that he will not allow City Hall to become a guarantor for the bridge's upkeep if he believes the guarantee is likely to be called on.
"I am committed to ensuring that no more of Londoners' taxes that I control will go to the Garden Bridge," said the Mayor.
"I will not allow any guarantees to be entered into for the maintenance and operation of the bridge unless I am convinced that this will not lead to further public expenditure down the line.
"It is up to the Garden Bridge Trust to demonstrate this in its business plan and any related documents.
"I have not set out specific requirements for how to do that, but the Garden Bridge Trust has already made clear its intention to develop an endowment fund, which would be one way of demonstrating it."
Caroline Pidgeon AM said: "At a painfully slow rate Sadiq Khan is beginning to learn that he does not have to provide a taxpayer-funded bailout for the ongoing maintenance and upkeep of the Garden Bridge."
"I just hope that he doesn't take much longer to finally realise that it is within his grasp to simply say 'no' to any taxpayer-funded guarantee being offered by the Greater London Authority."
"The sooner he makes that decision the better."
One of Boris Johnson's final actions before leaving City Hall was to reduce the fundraising threshold that the Garden Bridge Trust would have to reach before the bridge's future maintenance could be guaranteed by the taxpayer.
This guarantee was to be subject to "the trust demonstrating to the Mayor's satisfaction that it has secured a satisfactory level of funding to operate and maintain the Garden Bridge for at least the first five years from its completion".
After a decision signed by Boris Johnson just two weeks before the end of his mayoral term, the putative guarantee is now merely subject to the trust having a "satisfactory funding strategy" but with no requirement to actually raise the cash in advance.
Last month Mr Khan commissioned Dame Margaret Hodge MP to carry out an investigation into the Garden Bridge project.
Last week he told LBC radio that he faces a "conundrum" over the Garden Bridge project.