London mayor Sadiq Khan has ordered a review into Thomas Heatherwick’s proposed £185m Garden Bridge project, which will investigate whether taxpayers have had value for money for their contribution.

Dame Margaret Hodge MP, the former chair of the UK’s Public Accounts Committee, will conduct the review. She will focus on the procurement process around the project, and analyse whether the required standards have been met around transparency and openness. According to Khan, the review will push the project’s developers “to achieve higher standards of accountability and transparency [the project] has so far been lacking.”

The idea of a garden bridge across the River Thames between South Bank and Temple was first pitched by British actor Joanna Lumley and received strong backing from Khan’s predecessor Boris Johnson, before his tenure as mayor ended in May. However, the project has been mired in controversy over the procurement process, which saw Heatherwick Studio’s vision selected over competing bridge designs from Wilkinson Eyre and Marks Barfield.

According to an Architect's Journal investigation, Heatherwick was present for several meetings with mayoral staff, including Johnson, before the contest was held.

Khan has previously backed the project on the proviso that no new London taxpayers’ funds should be committed to and that it should be a genuinely public and open space with strict limitations on how often it is closed for private events. However, he has previously called for a full investigation into how the project has developed.

Now Hodge will assess the findings of previous reviews and interview current and former staff of Transport for London and the Greater London Authority to investigate the conduct of the organisations since the project was first proposed. The review, which will cost the taxpayer £25,000, will culminate in a report to the mayor setting out any lessons that should be learnt in order to improve the conduct of potential and approved projects in the future.

“I’m clear that since the beginning of the project there hasn’t been the necessary standard of transparency and openness around the Garden Bridge,” said Khan. “Nearly £40m of public money has already been spent on the Garden Bridge project, and Londoners deserve far more information about the decisions that have been made around how their money is being spent.

“Margaret Hodge is hugely respected for her work scrutinising some of the UK’s largest and most high-profile publicly funded bodies. There’s no better qualified person to get to the bottom of the procurement process around the Garden Bridge, and establish whether Londoners have been getting value for money since the project began."

Hodge said: “It’s not a project that I have previously had an opinion on either for or against, but given the millions of pounds of public money allocated to the project, it is clear that there needs to be far more transparency around how funds are being spent. The planned bridge is a major project in an iconic part of London, and there are clearly questions that remain unanswered around issues like procurement.”

In an interview with the BBC last month, Heatherwick hit back at critics of the bridge, stating that any rejection of the project at this stage would show that “we have suddenly become a society who have no confidence in ourselves”.

"There's all sorts of people who want to get their little agenda and pin it onto this project,” he said. “But it’s an amazing project. How can it possibly be a bad thing to stitch the city together better, to create new public space that we have never had before, to create new views for all of us?”

He added that decision-makers must “hold their nerve” over the project.

In its most recent public statement, the Garden Bridge Trust has said construction on the bridge is not now likely to start until next year. Land deals and an agreement with Coin Street Community Builders, leaseholder of the land earmarked for the bridge’s south landing point, must be reached before building work can begin.