New HS2 Chief Executive Mark Wild said the project is facing “a very serious situation” and is need of a “fundamental reset” in a bid to keep costs down to complete the rest of the route.

His comments came as a construction update revealed the majority of the deep tunnel drives and earthworks needed for the high-speed railway have now been completed.

Figures show that 70% of twin-bore tunnels have been excavated to date, representing 38 of the 55 miles being built for the railway.

In all, five out of 12 tunnel drives have been completed.

The update revealed that 58% of earthworks for the railway’s cuttings, embankments, stations and landscaping have been completed representing almost 92 million cubic metres of material moved in total so far.

Additionally work has started on construction of 158 out of 227 viaducts and bridges – 70% – with 13 already built.

But Wild – who joined the project at the start of December said: “HS2 represents a significant investment in Britain’s future and in the last month I’ve been inspired by the hugely impressive feats of civil engineering taking shape right along the route. New railways provide better journeys and they boost economic growth by fuelling investment in communities and businesses.

“The prize is clear. However, the programme is in a very serious situation that requires a fundamental reset to enable it to be delivered to the lowest feasible cost. I am committed to delivering this reset over the coming year to ensure the railway can be brought into service safely and efficiently.”