Completion of work in Crossrail’s tunnels has slowed as testing of trains is given priority, Transport for London board papers have revealed.

Papers released ahead of next week’s meeting called construction productivity on the delayed line “disappointing”.

“The completion of the rail systems infrastructure in the tunnels remains a key issue and productivity has been disappointing,” the commissioner’s report said.

A spokesman for Crossrail told Construction News the slowdown was due to a change in priorities.

Previously, construction had taken priority in the tunnels with dynamic testing of the trains being carried in short windows, but that had now switched around with testing being prioritised.

Testing is now taking place four days a week with construction being carried out in the remaining available time.

Tunnel work to be completed includes fire mains, low voltage networks, walkways and drainage.

“Any outstanding work remaining after the start of Main Dynamic Testing (MDT) will have to be undertaken around the testing programme,” the commissioner’s report added.

Dynamic testing started on 14 January with trains running at full speed. Crossrail reported the test was completed successfully.

Chief executive Mark Wild said the main testing getting under way was “an important step” for the project and that it would continue for another six months.

Over the coming weeks multiple trains will be tested on the system along with their transition to Network Rail’s infrastructure.

Crossrail, TfL and the operator MTR are currently reviewing the programme ahead of publishing a new opening date for the Elizabeth Line.

Contractors were able to demobilise at three further stations – Farringdon, Woolwich and Custom House – in December.

The £15bn project had been due to open in December 2018 but delays to construction work and systems testing scuppered the completion.

On 10 December a new funding package was agreed between TfL, the Greater London Authority and central government. Since July 2018 an extra £2.45bn has been made available to complete the line.

Around £1.3bn of this has been loaned to TfL via the GLA, which TfL will repay using funds raised from business rates and the community infrastructure levy.

This has created extra funding pressure for the proposed Crossrail 2 line, which is planned to be part funded by such revenue streams.