The heavily delayed Crossrail will not open as planned in summer 2021 because of delays caused by coronavirus, its board has said.

The troubled railway, from Berkshire to Essex via central London, was originally expected to open in December 2018 but repeated delays have pushed it back.

On Thursday evening, Crossrail said: “A programme of this scale and complexity was already challenging, the impact of Covid-19 has clearly made the existing pressures more acute.

“Due to a pause of physical activity on sites and significant constraints on ongoing work – time has been lost, only some of which can be recovered.

“The opening of the central section between Paddington and Abbey Wood next summer, as announced earlier this year prior to Covid-19, is not achievable.”

Crossrail did not provide a new date for when the railway line was now expected to be open, but said that a “more comprehensive update” would be issued in due course.

The high speed railway has been controversial ever since construction plans emerged more than 10 years ago.

Andy Byford, London’s new Transport Commissioner, said that the news was “hugely disappointing” and that he would leave “no stone unturned” in order to finish the project.

“Crossrail is a transformational project that will benefit London and beyond forever, and it is vitally important to get it over the line,” he said.

“The news that coronavirus and other factors mean the railway cannot now open next summer is hugely disappointing.

“Alongside leading TfL out of the current coronavirus crisis so that it can effectively support London’s recovery, opening the Elizabeth line is my top priority and I will leave no stone unturned to ensure this happens safely and reliably as soon as possible.”

Mark Wild, chief executive of Crossrail Ltd, said: “Everyone working on the Crossrail project knows London needs the Elizabeth line more than ever and we are doing everything possible to deliver the railway as safely and as quickly as we can.

“We have a comprehensive plan to complete the railway but existing schedule pressure along with Covid-19 has impacted the programme and time has been lost.

“Further work is being undertaken to finalise our detailed recovery plan which re-sequences the remaining work.

“Despite the challenges presented by Covid-19, good progress continues to be made with completing the remaining construction works, with much of this work coming to an end along with software testing for the signalling and train systems.

“The focus is completing the outstanding works across the tunnels, shafts and portals so that intensive operational testing can begin and the Elizabeth line can be delivered at the earliest opportunity.”