Cross-rail delays will cost TfL up to £ 1.35 billion in lost profits.

Delays to Crossrail will cost London up to £1.35bn in lost ticket revenue, according to the capital’s transport authority.

The shortfall in fare income will put further stress on Transport for London’s finances after the central government grant of about £700m a year was ended in 2018.

The opening of the £18bn Elizabeth line, as the completed Crossrail project will be known, is now expected in 2021, at least two years behind schedule and billions of pounds over its original £14.8bn budget.

TfL also warned that there were recent signs of lower passenger demand for public transport, possibly due to wider economic uncertainty, that could further threaten its income. However, TfL said it was still on track to run an operating surplus by 2022-23, with cost-cutting in its everyday operations saving more than £1bn annually.

It said it would continue investment in public transport, walking and cycling. But while some upgrades to the tube will go ahead, TfL said plans to overhaul the “life-expired“ signalling on the Piccadilly line, a major artery across London to Heathrow airport, could not restart without central government funding. The last government spending round made no commitment to any funds for TfL.

The mayor of London, Sadiq Khan, said: “I am hugely proud of what we have achieved improving transport across London – this is despite the ongoing economic uncertainty and the average reduction of £700m per year in TfL’s funding from central government.

“But London also needs a government that recognises the importance of continued investment in new infrastructure for the future of our economy, and it is essential the new government commits to working with us to deliver vital projects such as Crossrail 2 and the Bakerloo line extension.”

The TfL commissioner, Mike Brown, said he was working urgently to secure “steady, sustained funding in existing and new infrastructure” from the new government.

Crossrail remains TfL’s biggest headache, with delays adding significant additional capital investment and revenue pressures, the transport authority said. On Sunday one small milestone will be passed as TfL takes over the running of services to Reading from Paddington, a future western branch of the Elizabeth line.

Although many stations are near completion, Crossrail confirmed last month it would need more time to finish the signalling software, as well as months of testing that ruled out opening the central, underground section next year. It is now due to open “as soon as practically possible in 2021”.

That delay would spell an additional £500m and £750m in lost revenue for TfL over the next four years, on top of £600m already accounted for in the business plan issued in December 2018 when the first delays were known. TfL will also partially fund the escalating construction costs of Crossrail.