Hammond stopped short of committing to the current construction timetable.

But he said: “I think funding for Crossrail is already well established. We are making sure that in delivering the project we absolutely optimise value for money.”

Terry Morgan, chairman of Crossrail, said: “This is welcome news. To get such early and firm support from the government means the project can go forward with confidence.

“This construction project will mean a lot of jobs in London and the southeast and a boost for the wider UK economy as a whole.”

Fears had been growing that Crossrail could be an early victim of the new government’s bid to bring down the country’s £163bn debt mountain.

One civil engineer told the Enquirer: “This is certainly a positive statement but we are not out of the woods yet.

“The next worry is that the work programme could be slowed down as the government seeks to make savings.

“We have been waiting a long time for this project and the work is already well-advanced so we want to see the scheme push-ahead along the existing timetable so we can build this vital route across London.”

The project has already spent £2.5bn, and is committed to another £1.5bn of work.

Crossrail’s Morgan said the next major milestone for the project will come later this year when it will release a £2bn tender to dig five tunnels under the city.

Crossrail has been suppling the industry with a string of tender opportunities during the last 12 months.

The latest is the £40m Paddington Integrated Project where BAM Nutall, Bovis Lend Lease, Carillion, Laing O’Rourke, Morgan Est and Vinci have been shortlisted.

The source said: “You just have to look at the numbers and the flow of work to see how important this is to the industry. It’s as big as the Olympics for civil engineers.”