The committee’s latest report into the high speed rail programme highlights that the scheme is currently estimated to cost up to £88Bn in 2015 prices, significantly more than the original budget of £55.7Bn.

“We are unconvinced that there will not be further cost increases, such as those we have seen on Crossrail and many other programmes, especially given that the route and forecast cost of the northern sections of the proposed railway is still very uncertain and will remain so for years to come,” the report says.

In addition, it emphasises that the project is now using a revised commercial model with its main civil contractors, which means High Speed 2 bears more of the risk of cost increases.

Also criticised by the committee are the Department for Transport and HS2 Ltd’s transparency regarding delays and budget overruns, which the report says has undermined public confidence in the programme.

Public Accounts Committee chair Meg Hillier said: “The committee is concerned about how open the Department and HS2 Ltd executives have been in their account of this project. It is massively over budget and delayed before work has even begun. There is no excuse for hiding the nature and extent of the problems the project was facing from Parliament and the taxpayer.”

The report also expresses concern that lessons from the delivery of other major projects are still not being learned by the Department.

“The Government unfortunately has a wealth of mistakes on major transport infrastructure to learn from, but it does not give confidence that it is finally going to take those lessons when this is its approach,” Meg Hillier added.

“In the six monthly reports the Department has now agreed to give us, we want to see an honest, open account, and evidence of learning from past mistakes being applied to bring this project under control, to deliver it within the timeline and budget that have been agreed in justifying the project.”

Responding to the criticism, a Department for Transport spokesman said: “The current Secretary of State has been clear that this project must go forward with a new approach to Parliamentary reporting, with clear transparency, strengthened accountability to Ministers, and tight control of costs.

“We have comprehensively reset the HS2 programme, introducing a revised budget and funding regime, with significant reforms to ensure the project is delivered in a more disciplined and transparent manner.”

The Department also rejected claims that it has not learned lessons from previous work on High Speed 2 and from issues experienced on other major projects, including Crossrail.

(Photograph: Grimshaw Architects)