Main civils was originally planned to start in in November 2018. This slipped to March before being extended to June in order to provide suppliers with additional time to optimise their designs.

Now HS2 chiefs have put this date back again to after the summer to give contractors more time on costings.

The project is reported to be around £1bn over the £6.6bn budget and HS2 bosses want contractors to streamline final costs before signing off contracts for the construction phase.

An HS2 spokesperson said: “We continue to negotiate with our main civils contractors and will move to notice to proceed when those negotiations are concluded later this year.”

He added that HS2 was well advanced on enabling works.

The spokesperson said: “HS2 already supports more than 7,000 jobs both directly and across our UK-wide supply chain.

“Work has been carried out on more than 60 sites including major works ongoing at Euston, Old Oak Common and Curzon Street in Birmingham. ”

The joint ventures seeking final sign-off are:

• SCS JV (Skanska, Costain, STRABAG)
• Align JV (Bouygues, VolkerFitzpatrick, Sir Robert McAlpine)
• CEK JV (Eiffage, Kier)
• BBV JV (Balfour Beatty Group, VINCI)

One contractor told the Enquirer: “It’s starting to look like the start could be a year later than originally planned, we shall see.”

Last week HS2 started tendering to appoint two consultants to help beef up project control and cost management on the project.

It is on the hunt for a control partner to support baseline management, programme planning, reporting and risk management. The selected firm will supply cost and estimating services as part of a deal worth around £125m over eight years.

HS2 is also looking for a separate consultant to support commercial management on the project. This will involve pre-contract development and post-contract management support, as well as developing and communicating HS2’s commercial procedures, processes and systems.