The taxpayer must cover a £160 million shortfall in private-sector funding for the Crossrail project after the Department for Transport failed to secure the expected contribution from Heathrow, a report revealed today.

Plans for the £14.8 billion rail line envisaged a £230 million contribution from Heathrow, to reflect the benefit it is expected to gain from the link to central London, Maidenhead in Berkshire, and Brentwood in Essex.

But Heathrow’s regulator, the Civil Aviation Authority, calculated that with the airport already running at or near capacity, Crossrail would deliver no net benefit in terms of additional passengers. After the CAA set aside a provisional pot of £100 million, the DfT lowered its proposal to £137 million, but this month the regulator decided that Heathrow’s contribution will be just £70 million.

The shortfall means that the DfT’s contribution to the project will rise from £4.8 billion to almost £5 billion, but this remains inside the £5.2 billion set aside in case it failed to secure sufficient funding from private sources, said spending watchdog the National Audit Office.

It found that taxpayers’ interests had been “well protected” in the project, which is “on course to achieve value for money” and to be fully open by its promised 2019 delivery date.