Crossrail's Elizabeth Line is one of the largest single infrastructure investments ever undertaken in the UK - a £15bn transport project that was due to open in December 2018 but now delayed to autumn 2019.

New Crossrail delays could cost Transport for London at least £600m, according to Moody’s.

This is set to put TfL under “significant financial strain,” according to the report.

An investigation has been launched into the project by the National Audit Office.

Workers use a laptop computer as they inspect a rail tunnel wall at Whitechapel station, developed by Crossrail, beneath London, U.K., on Friday, April 4, 2014.
London’s Crossrail is set to link 40 stations from east to west across the capital Credit: Bloomberg via Getty Images

Last month, a report by the London Assembly revealed that TfL will miss out on around £210m of revenue due to the line’s delayed opening.

Moody’s estimates that a further £400 million will be lost.

They expect the worst impact from this to be seen between 2020 and 2021.

This is when TfL would lose its planned operating surplus and £400m of expected revenue.

Moody’s Vice President, Zoe Jankel, said this set-back is one of a number of challenges for Transport for London.

“Overall, we expect that TfL will be able to manage the impact of the delay.  However, this will weaken its ability to cope with any other unforeseen costs or revenue shortfalls.”

Londoners and commuters walk past the billboards promoting Crossrail's new Queen Elizabeth rail line, the capital's newest on 3rd September 2018, on Moorgate in London, England.
At 73 miles long London’s Crossrail is the biggest construction project in Europe. Credit: In Pictures via Getty Images

Early this year, the government announced that funding for the project had increased from £14.8bn to £15.4bn. This figure did not include the additional cash needed to complete remaining work on its central section.

Additionally, TfL were given an extra £350m loan by the government to support construction on the project.

There is currently a nine-month delay to the opening of the line. The project, officially known as The Elizabeth Line, will begin operating in Autumn 2019. It was originally set to begin operating this December.