The controversial Thomas Heatherwick-designed Garden Bridge is to come under further scrutiny, as London mayor Sadiq Khan has announced a review to assess whether the project provides value for money.

The inquiry will look at whether the bridge proposed across London's River Thames has been a suitable use of public money, and review whether governmental departments dealt with the project appropriately.

The 367-metre-long structure is currently expected to cost £185 million, with £60 million pledged by the government. Almost £40 million of that has already been spent.

But if the report concludes that the 367-metre-long bridge doesn't offer value to the taxpayer, it could prompt Khan to reconsider his support for the project.

The mayor has already pledged that no more public funds would go towards the structure, which is billed as a "beautiful new garden floating above the River Thames".

"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," he said.

"Nearly £40 million 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.

The inquiry will be led by Margaret Hodge, the former chair of parliament's public accounts committee, who recently published a book about wasteful spending by the UK government.

Khan said it will help the project "achieve higher standards of accountability and transparency it has so far been lacking".

"Margaret Hodge is hugely respected for her work scrutinising some of the UK's largest and most high-profile publicly funded bodies," said Khan.

"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."

British designer Thomas Heatherwick first unveiled his design for the Garden Bridge in 2013.

It is set to be constructed between Temple and the South Bank, with full-size trees and planted sections along its deck, and a "super-strength" copper-nickel skin covering the structure's underside and legs.

But the project has been mired in controversy. Questions have been raised over the procurement process for the design of the bridge, with some believing that Heatherwick was given an unfair advantage over other firms that bid on the project.

Access to the bridge has also caused issues, with campaigners protesting against lack of bicycle access and the fact that the structure will be closed to the public at night and for 12 days each year.

Alternative green crossings have been proposed by architects Allies and Morrison, and Crispin Wride for nearby Blackfriars Bridge, along with a variety of more satirical suggestions.

Heatherwick also has a similar project in New York – the Pier 55 elevated park over the Hudson River, which has begun construction after overcoming a legal battle earlier this year.