HS2: Cost of building line between London and Birmingham could reach £66bn

HS2 Ltd executive chairman Sir Jon Thompson claimed the initial estimate was “too low” and based on rough plans, but there have also been numerous changes to the project, “poor delivery” and inflation.

He said the estimated cost for Phase 1 is between £49bn and £56.6bn at 2019 prices, but adjusting the range for current prices involves “adding somewhere between £8bn and £10bn”.

Speaking to the Transport Committee, he also said the government’s plan to run HS2 services on the existing line between Birmingham and Manchester will result in slower journeys with less capacity, unless several stations are extended to accommodate longer trains.

He said the HS2 trains have fewer seats than services currently run by Avanti and they have to travel slower around bends because they do not tilt.

In 2013, HS2 was estimated to cost £37.5bn (in 2009 prices) for the entire planned network, including now-scrapped extensions from Birmingham to Manchester and Leeds.

But Sir John said that estimate “was poor” as it was based on “very, very immature data”.

“You don’t have a design, you haven’t procured anything, there is no detail on which you can cost anything,” he added.

“If you say to a builder, can you give me a quote for an extension, they walk around and say ‘it’s £50,000-something’.

“But then you get into the detailed design, you know exactly how big it is, what surfaces you want, how much concrete needs to be poured. Unsurprisingly you get a better number.”

Following Prime Minister Rishi Sunak’s decision in to axe the northern leg of HS2, he published a plan called Network North which stated phase one could cost as little as £45bn and open by 2033.

Sir John accepted plans are being altered to cut costs but added: “Whether it’ll come down by anything like the number that was quoted in Network North, I doubt”.

In October, the Department for Transport said it would begin selling off land bought to pave the way for phase 2a (Birmingham to Crewe) within “weeks”.

Land safeguarded for phase 2b, which was originally due to connect Birmingham to Manchester and Leeds, is due to be released in July.

HS2 Ltd has already spent more than £2bn on buying land and properties for phase 1 (London to Birmingham), and more than £219m for phase 2a and £368m for phase 2b.

In Leeds, more than 700 hectares of land is currently being safeguarded for HS2 and some of it is worth more than £8m per hectare.

The Government said it will "allow for alternative investment in these areas" and it is "untrue to claim land will be sold off cheaply or in a hurry".

But political leaders in the north are concerned the move will prevent future governments from reviving HS2 or building a new north-south rail line that provides additional capacity.