The future of the Garden Bridge in London may be in jeopardy after accounts published by its trustees said costs could ‘substantially exceed’ the £185M estimate and that the trust set up to deliver it may no longer be a ’going concern’.

The accounts lodged with Companies House stated that ”due to material uncertainties in existence ahead of finalising these accounts, trustees are unable to conclude that the trust is a going concern” and felt it appropriate to flag the risks in the report.

The accounts, for the year ending March 2016, said that the trust hoped the uncertainties would be resolved over the months ahead but since a number of these matters were outside the trustees’ control, it recognised it may have to consider further delays to the project or decide if the project remained viable.

Delays such as the judicial reviews of local council decisions, Brexit, a change in government and protracted negotiations with third parties, it said, had led to an increase in cost.

As part of the financial section of the report, it stated that the total project cost was £185M, but said that ”due to hurdles still to be cleared and the ensuring delays the final cost could substantially exceed the formal estimate”. It went on to say that until the hurdles had been cleared, it would not obtain a definite amount for any increase. It said it needed to increase the unrestricted funding and underwriting available and secure the remaining private sector funding.

To date, it said it had secured £69M of private funding and £60M of public funding from the Department for Transport (DfT) and Transport for London (TfL), £20M of which was being treated as a loan which would be repayable to TfL.

A joint venture comprising Bouygyes TP and Cimolai was appointed in April 2015 to build the bridge with consultant Arup undertaking the detailed design. However it said that to reduce expenditure it had put the construction contractor on standby as of July 2016.

Before construction can start, it said that it still had to secure rights to the necessary land on both sides of the river and complete the associated planning requirements. While the previous London mayor had committed to providing a guarantee for the future maintenance and operations of the bridge, it said was awaiting the new mayor’s – Sadiq Khan – decision to honour the commitment.

However despite backing the project, in September last year, Khan ordered a review of the bridge examining whether the project offered taxpayers value for money and investigating the work of several stakeholders.

Despite raising its concerns about funding for the bridge, Garden Bridge Trust chairman Lord Davies said he still expected construction to start in 2017.

“The Garden Bridge Trust has made significant progress to get to a stage where we have completed detailed pre-construction work and have a contractor on board,” said Davies.

“We have consistently flagged the areas of risk to the project about acquiring land, the signing of the Mayoral Guarantee, our funding position and the cost of the project. These matters are dependent on third parties and are outside trustees’ control and have led to delays. The Trustees are duty bound to disclose these risks and how we intend to deal with them, in this report.

“We strongly believe we can progress all outstanding issues and we are determined to make the project happen. We look forward to working with our supporters, including the Mayor and the Government to make the Garden Bridge a reality.

“We expect to start construction in 2017.”

The trust needs to raise sufficient additional funding in enough time to agree the contract with the joint venture and for work to commence before current planning consents expire in December 2017.