Dame Margaret Hodge has published her report into the Garden Bridge project, finding that "too many things went wrong" and recommending that the Mayor accepts the financial hit from cancelling the scheme.
Last September Mayor of London Sadiq Khan commissioned Dame Margaret Hodge MP, former chair of the public accounts committee, to examine the value for money of the proposed Garden Bridge across the Thames between the South Bank and Temple.
Dame Margaret concludes that:
• Decisions on the Garden Bridge were driven by electoral cycles rather than value for money
• The cost of the bridge has spiralled from £60 million to a likely final cost of more than £200 million
• I am firmly of the view that more public money will be needed to complete the construction
• Contracts awarded by Transport for London to Arup and Heatherwick Studio were not open, fair or competitive procurements
• The business case was constructed after contracts had already been awarded.
• Throughout my review, the only people to express support for the Garden Bridge were the Trust itself, the Evening Standard and Boris Johnson
• The goalposts have moved several times and the risks to the taxpayer have intensified
She also complains that Boris Johnson, former Mayor of London and now foreign secretary, refused to cooperate with the review.
Commenting on her report, Dame Margaret said: "I did not seek to ask whether the concept of a garden bridge over the River Thames is a good idea. But my review has found that too many things went wrong in the development and implementation of the Garden Bridge Project.
"Value for money for the taxpayer has not been secured. It would be better for the taxpayer to accept the financial loss of cancelling the project than to risk the potential uncertain additional costs to the public purse if the project proceeds.
"In the present climate, with continuing pressures on public spending, it is difficult to justify further public investment in the Garden Bridge.
"I would urge the Mayor not to sign any guarantees until it is confirmed that the private capital and revenue monies have been secured by the Garden Bridge Trust.
"My report outlines some key lessons that can be learned from the Garden Bridge project across different public organisations and makes a number of recommendations. I thank the Mayor, Sadiq Khan, for giving me the opportunity to examine the project in detail."
Responding to the report, Lord Davies, chairman of the Garden Bridge Trust, said: "We are pleased that Dame Margaret has finally published her report after six months of uncertainty.
"We will be studying the report in detail and seeking a meeting with the Mayor of London 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."
Bishop's ward Labour councillors Jenny Mosley and Kevin Craig told us that they "wholeheartedly support the findings of the report".
"We have high hopes that the Mayor will implement the recommendations of the report, significantly to not provide the £3 million a year guarantee to the GBT and to carry out a full assessment of GLA/TfL controls recommended by Margaret Hodge's report," said the councillors in a joint statement.
They also called for the resignation of Lord Davies as chair of the GBT and the winding up of the charity, as well as a full public inquiry into the use of public funds on the project.
Michael Ball, chair of the Thames Central Open Spaces campaign group which has led local opposition to the scheme, said: "Sadiq Khan must finally stop dithering and scrap the sinking Garden Bridge, following Dame Margaret Hodge's damning report."
He added: "Sadiq commissioned Hodge to undertake a comprehensive review of the project, and he can't ignore its withering conclusions.
"It's time Sadiq represented the people who elected him and started protecting their pockets from being picked any further by announcing his refusal to pay out any further to the project, and undertaking a root and branch review of the UK's highest-spending single public authority."
Caroline Pidgeon, Liberal Democrat London Assembly member, said: "Dame Margaret Hodge is crystal clear when she states that the Mayor should not sign any taxpayer funded guarantees until it is confirmed that the private capital money to build the bridge has been secured by the Garden Bridge Trust.
"This is the final nail in the coffin of the Garden Bridge. The Mayor should put us out of our misery and pull the plug on this project."
City Hall has also made public a series of letters exchanged last autumn between Lord Davies, chair of the Garden Bridge Trust, and Mayor of London Sadiq Khan.
In the correspondence Mr Khan confirms that he has no objection in principal to providing a guarantee for the upkeep of the bridge from public funds, and describes himself as a supporter of the Garden Bridge project.
The Mayor also tells the trust that he does not see how Dame Margaret could possibly fail to reach the conclusion that taxpayers would be best served by continuing with construction of the bridge.