A government spending watchdog has warned that the controversial Garden Bridge could result in the loss of more than £22 million in taxpayers' money.
An investigation by the National Audit Office (NAO) said there was a "significant risk" that the project will not go ahead as the trust responsible for building the bridge had still not secured the land it needs on the south side of the river.
If the project were to be scrapped, the NAO estimated that £22.5 million of the £30 million already invested in the bridge by the Department for Transport would be lost.
The watchdog also found that ministers twice overrode the advice of officials to extend funding to the bridge - despite an initial assessment concluding there was a high risk that the bridge could represent "poor value for money".
On one occasion occasion, the then Prime Minister David Cameron personally intervened to get more taxpayer money allocated to the project. Pressure from No. 10 eventually resulted in the then transport secretary Sir Patrick McLoughlin ordering officials to underwrite £15 million worth of cancellation liabilities.
The findings come after current mayor Sadiq Khan ordered an investigation into the spending on the project by his predecessor, Boris Johnson.
The chair of the Public Accounts Commitee, which oversees the NAO's work, said she was 'worried' about the findings.
Government ministers have also agreed that further risk to the taxpayer from the project must be curtailed.