Crossrail 2 backers must “think creatively about funding options” an infrastructure expert has warned, after Transport for London (TfL) revealed progress on the scheme had slowed.

London First infrastructure director David Leam told New Civil Engineer a delay to Crossrail 2’s schedule would allow the project team to find savings on the £31bn scheme. Last year Arup and Mott MacDonald won a £3M contract to drive down costs on the proposed mega-project.

Leam said he expected the “decision point” for Crossrail 2 to be included in the autumn Budget later this year.

“I think in any world there will be a need to think creatively about funding options,” said Leam, adding there is plenty of work to be done between now and the autumn.

“If it was just, ‘you’ve got to sit tight until November’, and we were all just sat on our hands, that would be a problem but I don’t think that’s the case.”

A public consultation on Crossrail 2 was originally scheduled to begin early this year. However, it has been pushed back until the end of 2018 after TfL director of city planning Alex Williams revealed a government-sought independent financing review would not report its findings until the autumn.

The independent financing review is looking at how to reduce costs on the £31bn scheme, for which London has been asked to pay half during construction. TfL submitted its reworked Crossrail 2 proposal to the government in November last year.

On Friday Rail Industry Association (RIA) chief executive Darren Caplan warned congestion would increase on London’s transport networks unless progress is made on Crossrail 2.

Caplan said: “Most people looking at this will wonder what has changed since Transport Secretary Chris Grayling and London Mayor Sadiq Khan offered together their full throttle support to this vital infrastructure project just six months ago.

“Simply, this project should not be delayed without good reason, and it’s difficult to understand what good reason exists now.”

During a recent London Assembly transport committee meeting, Williams described Crossrail 2 as the “jewel in the crown” of the Mayor’s Transport Strategy and the London Plan.

Deputy mayor for transport Val Shawcross added that finding 50% of the £31bn costs for Crossrail 2 would be challenging, but TfL is confident it can be achieved.

“It seems to be a long, slow process but it’s still moving in the right direction,” she said.

A TfL spokesperson said: “TfL and the DfT (Department for Transport) are working together to agree the terms of reference for the independent financing review.”