Transport for London (TfL) is to lose a further £10m in advertising from the delay to the opening of Crossrail, City A.M. can reveal.

The £15.4bn Elizabeth Line was due to open this December but has been delayed until next autumn because of safety concerns and delays to signalling testing.

TfL was relying on the line – billed as the biggest infrastructure project in Europe – to bring in additional revenue through ticket fares to plug a hole in its £1bn deficit.

TfL commissioner Mike Brown admitted earlier this month that the transport body would miss out on £20m in additional revenue through ticket fares.

Read more: TfL to lose £20m in revenue from Elizabeth Line delay

In a letter to Caroline Pidgeon, chair of the London Assembly's transport committee, Sadiq Khan's deputy mayor for transport Heidi Alexander has said TfL will also lose out on an additional £10m from commercial income, or advertising.

Pidgeon said: "The £10m in lost commercial income due to the delayed opening of Crossrail is just the latest blow to TfL's finances.

"Any examination of TfL's accounts shows that it is clearly on the ropes. In its current state I wonder how many more financial blows it can now take."

A TfL spokesperson said: "We are assessing the revenue implications. Details of how we will manage the change will be announced as part of our annual business planning process at the end of 2018."

The line, which will run from Reading and Heathrow in the west through tunnels in central London to Shenfield and Abbey Wood in the east, was a key part of TfL's business plan, with it being forecast to bring in £151m in the 2018/19 financial year and £3bn within five years.

Read more: Crossrail chairman will not step down in wake of Elizabeth Line delay