The Garden Bridge has been criticised by an independent review which highlighted escalating costs, a weak business case and "little regard" for value for money, and advised that the project should be scrapped.
The report by senior Labour MP Dame Margaret Hodge, assessing the value for taxpayer money from the controversial project, was commissioned by mayor Sadiq Khan in October 2016.
Hodge said costs have escalated from an early estimate of £60m to £200m today and "are likely to increase further", and that the risk to the taxpayer has grown since the original aim to fund the Garden Bridge through private finance has been abandoned.
She said it would be "difficult to justify" giving any further cash while the Trust's finances were in such a "precarious" state and called on the mayor not to sign any guarantees until funding is secured.
The Garden Bridge Trust has lost two major private donors and has pledges of £69m with no new pledges secured since August 2016.
The pedestrian crossing over the Thames faces a funding gap of at least £70m with costs rising past £200m after donors dropped out.
From its inception when there was confusion as to its purpose, through a weak business case that was constructed after contracts had been let and money had been spent, little regard has been had to value for money.
Hodge was not asked to consider whether the bridge was a good idea at all, but rather whether it was value for money for the public funds.
A spokesperson for the mayor said: "The mayor wants to thank Dame Margaret Hodge for this thorough report, which raises some very serious questions about the way the project has been handled. The mayor will now take some time to carefully consider it and its implications.
"The mayor has been absolutely clear that he will not spend any more of London taxpayers' funds on the Garden Bridge. It is the Garden Bridge Trust that remains responsible for raising the necessary funds, and delivering the project."
The report also criticised the two Transport for London (TfL) procurements for the Garden Bridge, saying neither were open, fair or competitive and that Hodge's review had "revealed systemic failures and ineffective control systems at many levels".
The mayor's spokesperson said: "These were concerns that the current mayor shared when he came into office and from day one he sought to address them. A key part of this was putting in place a new, stronger TfL board with a greater ability to provide proper oversight and scrutiny over decision-making."
The project was originally backed by Sadiq Khan's predecessor Boris Johnson.
Lord Mervyn Davies, chairman of the Garden Bridge Trust, said: “We will be studying the report in detail and seeking a meeting with the mayor to discuss next steps. The Trust remains as determined as ever to make the Garden Bridge happen which will bring huge benefits to London and the UK.”
Opinion over the review has been divided...
A kangaroo court judgement
Conservative London Assembly member Andrew Boff said:
Personally I have long opposed the Garden Bridge but the angle of criticism over the process is wildly off the mark. It’s entirely wrong to say the advancement of the project was politically motivated at the taxpayers’ expense.
This is a kangaroo court judgement that lacks transparency and bases its verdicts on draft reports of the internal audit, not the final conclusions.
The final nail in the coffin
Labour London Assembly member Tom Copley, said:
Given today’s report quite clearly states that it would be better to cancel the project than to risk the potential uncertain additional cost to the taxpayer, this must surely be the final nail in the coffin for the Garden Bridge.
Even if the Garden Bridge Trust raise the necessary funds for completion, it’s highly questionable they’d raise the revenue needed to meet the maintenance costs. We cannot leave Londoners exposed to the risk of having to pick up the bill.