The future of the Garden Bridge hangs in the balance after London’s mayor Sadiq Khan suspended preparatory work to allow City Hall to review the finances of the £175 million scheme.
Mr Khan has expressed support for the bridge but said he would not provide any more public money towards its construction.
The Department of Transport and City Hall have already agreed to pay £60 million towards the construction of the 366-metre bridge, but Transport for London (TfL) was expected approve an extra £3 million last Friday.
The money was to be used to improve and strengthen Temple tube station so its roof could withstand the weight of the north end of the bridge.
The mayor’s office said work on the tube station had been halted because it had been authorised just weeks before he was elected in May.
A spokesperson for Sadiq Khan said: “The previous mayor first approved plans for enabling work to prepare Temple tube station for the arrival of the Garden Bridge two years ago in the summer of 2014, but final authorisation was only provided in March this year, two months before the mayoral election.
“This enabling work has since been suspended and that was reported to the finance and policy committee last week.
“Sadiq Khan has been clear that no new public funds should be committed to the Garden Bridge and he has pledged to make the project more open and transparent – standards that were not always met under the previous administration.”
The charitable body behind the scheme, the Garden Bridge Trust, said the work on the tube station was part of a £20 million loan agreed with TfL, which is to be paid back on an agreed payment schedule that began in June.
A spokeswoman said work on Temple was paused “whilst the trust completes all required planning and land matters ahead of starting full construction”.
She said the trust was confident the finance and policy committee would not find issues with spending, and that the scheme was “full steam ahead”.
“Once all planning and property matters have been resolved, the next phase of the London Underground work will commence. All works will be paid for by the trust,” she added.
According to data published by City Hall in May, TfL is contributing £30 million, two-thirds of which will be returned by the loan.
Another £30 million is coming from the Department for Transport, whilst charitable foundations, corporate donors and philanthropists are providing another £83 million.
A further £32 million is needed to reach the £175 million target.
Earlier this week Caroline Pidgeon, the sole Liberal Democrat on the London Assembly, wrote to the TfL committee’s chairman, John Armitt, to express concern about the £3 million spend on Temple.
“The fact that this work to Temple station has been suspended at the 11th hour suggests that for too long TfL has not been in full control of public money it has been allocating to the Garden Bridge,” she said.
She also questioned the pledge to underwrite the bridge’s annual maintenance cost, expected to come to £3.5 million, made by the previous London mayor, Boris Johnson.
‘‘If the Mayor is really serious about ensuring that no further public funds are allocated to the Garden Bridge, his next step must be to immediately rip up the maintenance guarantee decisions that Boris Johnson foolishly signed up to.
“The lack of transparency over almost every aspect of the Garden Bridge cannot continue,” she said.
Designed by Thomas Heatherwick and championed by actress Joanna Lumley, the bridge has been mired in controversy since it was proposed in 2012.
It has been criticised for its use of public funding, and its governance has been called into question. The National Audit Office is examining the Department for Transport’s control over its grant, and the Charity Commission is investigating complaints made by MP for Vauxhall, Kate Hoey.