Mayor of London Sadiq Khan has reaffirmed his support for the Garden Bridge, despite concerns raised by some of his Labour colleagues at City Hall.
Mr Khan was challenged at Mayor's Question Time on Wednesday by Labour London Assembly members Florence Eshalomi and Tom Copley who warned that the case for the bridge had not been made.
Sadiq Khan said: "From the point at which I became Mayor, it was quite clearly in London taxpayers' financial interest to complete the Garden Bridge project.
"It would simply cost Londoners more to cancel the project now, than it would to finish building the Garden Bridge.
"If the bridge was cancelled now taxpayers will have spent £37.7 million for no benefit at all. However if we complete the project and our loan is repaid in full then the ultimate cost to taxpayers will be under half that cost at £18 million.
"So I will support the building of the Garden Bridge, but I am demanding that the project is made more accessible and open to all Londoners in return.
"I expect the Garden Bridge Trust to ensure that the Bridge be closed fewer days each year for private fundraising events and fewer hours when they do. I also want a guarantee that an ongoing programme of visits will be laid on for local school children."
Florence Eshalomi AM said: "Residents in Lambeth have raised serious concerns about the impact that the bridge and its construction will have on the South Bank area. I welcome that the Mayor has said he will take a much more open and transparent approach to the project, as it is vital those concerns are listened to and acted upon.
"I am still to be convinced that the Garden Bridge is the best use of taxpayers' money but it is clear that the previous Mayor has made it incredibly hard for the project not to go ahead without massive losses to the taxpayer.
"That said, I am especially concerned that Londoners will have to foot the bill if the Garden Bridge Trust is unable to drum up all the necessary funding. We need clarity from the Mayor and the Garden Bridge Trust on what will happen under these circumstances.
"The Garden Bridge is primarily a tourist attraction, it is not a transport scheme. Despite claims that it will promote and improve wildlife and biodiversity in London, no environmental charity has yet supported the project."
In a statement, the Garden Bridge Trust said: "We welcome the Mayor's support and look forward to working with him to make the Garden Bridge happen and deliver its many benefits to millions of Londoners and visitors to the city.
"We share the Mayor's desire to keep the bridge open to everyone for as long as possible and we have already taken steps to address this.
"The public money that has been spent so far has been used by the trust to develop the scheme to the stage where we have appointed a contractor, detailed design work has taken place and the bridge has secured planning permission. That work is crucial in enabling the project to secure large investment from the private sector.
"The £37.7 million of public money that has been spent since the project began includes securing necessary consents, progressing detailed design work, undertaking ground and river investigations, professional fees and developing parts of the bridge off-site."
Meanwhile Waterloo resident Jenny O'Neill – of the Thames Central Open Spaces campaign (TCOS) is launching a High court challenge against Lambeth Council's decision to allow its land on the South Bank to be leased to the Garden Bridge Trust.
"I have been particularly aggrieved at the manner in which this proposal has been handled by Lambeth Council, with one councillor taking the decision in private, despite numerous promises that this would be a public decision taken at a public meeting where the public could make clear their opposition," said Ms O'Neill.
"The manner in which Lambeth have sought to avoid its responsibilities towards Assets of Community Value and its role as our custodian of open space is despicable.
"Decisions as important as this need to be taken properly and got right, for Londoners now and for coming generations."