Crossrail will not open before December 2020, the company behind the infrastructure project has confirmed.

The project, which costs Londoners £30million a week, had its launch date officially pushed back for the third time on Thursday, April 25, following leaks from a senior source earlier this month who claimed works were still two years off completion.

Those hoping to catch the linked up Elizabeth line across London have now been given a “sixth-month window” opening date of between the end of 2020 and March 2021.

A new leadership team at Crossrail said it carried out a full audit of what went wrong in the past and has produced a “robust and realistic” plan to put Europe’s most ambitious and complex infrastructure project back on track.

The new proposals have required identifying and re-sequencing of more than 100,000 interdependent tasks and takes full account of exactly what has to be done and how long it will take.

Four main tasks need to be completed before opening including: building and testing the software to integrate the train operation system with three different signalling systems; installing and testing vital station systems, and installing equipment in the tunnels.

After this train trials will be undertaken to test the route and “shake out any problems”.

Mark Wild, chief executive of Crossrail, said: “I share the frustration of Londoners that the huge benefits of the Elizabeth line are not yet with us.

“But this plan allows Crossrail and its contractors to put the project back on track to deliver the Elizabeth line.

“Crossrail is an immensely complex project and there will be challenges ahead particularly with the testing of the train and signalling systems but the Elizabeth line is going to be incredible for London and really will be worth the wait - this new plan will get us there and allow this fantastic new railway to open around the end of next year.”

Tony Meggs, Crossrail chairman, added: “Both the Crossrail board and the Crossrail leadership team fully recognise the seriousness of the challenges we face.

“It is pleased with the progress by the new Crossrail leadership team to get a grip on the project and pull together a robust and realistic plan to complete the Elizabeth line.

“The Crossrail board will be holding the leadership team to account as they work to complete the railway - we will be open and transparent about our progress and will be providing Londoners and London businesses with regular updates as we seek to rebuild trust with all our stakeholders.”

News of the Crossrail opening date was announced just days after the publication of a London Assembly Transport Committee report titled: ‘Derailed: Getting Crossrail back on track’, which looked into the circumstances leading up to the delay and what lessons should be learned.

In response to the new Crossrail plan, Chairwoman of the London Assembly’s Transport Committee, Caroline Pidgeon MBE, said: “We welcome this announcement with cautionary relief.

“However, the project has been pushed back twice already, so the question has to be asked – is the ‘six-month window’ a hedge-betting exercise to avoid disappointing passengers once more?

“It is also incredibly frustrating that no senior executives will accept any responsibility for the litany of failures that have led to this delay.

“Londoners are forking out £30million a week to bring Crossrail to completion – further delays and doubtful dates are simply not an option.

“Crossrail will be a huge benefit to Londoners when it eventually opens.

“However, Transport for London, Crossrail and the Mayor all need to get their acts together to finish this project. We will be watching closely to ensure Londoners are not disappointed once more.”