Don't axe Garden Bridge, says trust chair Lord Davies

The chair of the trust behind London's controversial Garden Bridge has urged the government not to axe the project, after a Newsnight investigation revealed a £20m hole in its finances.

Lord Davies said "it would be a tragedy if the government withdrew their support now".

The Department for Transport has agreed to £30m in public funds.

It is currently considering whether to extend its £15m underwriting of the bridge.

A further £30 million will come from Transport for London.

Speaking to Newsnight, Lord Davies said that delays to the project had increased its cost by £10m to £185m, and conceded that the trust had raised £15m less than previously claimed.

The tree-covered Garden Bridge would span the Thames between Temple and the South Bank

Having publically stated for over a year that fundraising was progressing well and the project was short of £30m, the trust have now confirmed that in fact a further £56m is still needed from private donors for the project to go ahead.

Newsnight has learned that several funders have pulled out over the last year, with the Garden Bridge Trust explaining that "last year a small number of pledges made by interested organisations did not progress to formal funding contracts".

Lord Davies also admitted that the bridge would not be completed until 2019, a year later than currently scheduled.

However, he insisted the project had "momentum" and that the trust was confident it could raise the outstanding funds. "This is an iconic project. It does sum up what's great about Britain."

Plans propose more than 270 trees and 2,000 shrubs would be planted on the bridge

The proposal for a new bridge over the Thames has been beset by controversy. Transport for London have conceded that the procurement process was neither as open or fair as it should have been.

The Garden Bridge was conceived of by the actress Joanna Lumley as a memorial to Princess Diana. It was championed by Boris Johnson as London mayor and by George Osborne as chancellor.

But Sadiq Khan, the current mayor of London, has said there can be no more support from Transport for London or the Greater London Authority beyond the £30m they are contributing. He also said he believes it would be more expensive to cancel the project than to continue.

The plan is for the bridge to run between Temple Underground Station and the South Bank, and for it to be covered in trees and shrubs.

The designer of the project, Thomas Heatherwick, defended the scheme, and said politics must not get in the way.

"Money has been spent to get this far. It is ready to go, and it is important that our society doesn't show that we suddenly have no confidence in ourselves... that we don't suddenly seem like, 'Yep, we've had a political turmoil, now we suddenly close up and we're just going to go backwards.'"

"There's all sorts of people who want to get their little agenda... 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, new views for all of us."

Mr Heatherwick told the BBC it was important that all sides "hold their nerve".