The official estimated cost of HS2 is £72 to £98billion, compared with an original £55.7billion budget at 2015 prices. Rail experts have suggested the final total could balloon.
The committee accused the Department for Transport and HS2 Ltd of a lack of transparency when the project’s delivery times and budget were hit with “serious issues”.
They claimed the DFT and rail bosses could not tell them how they would deliver promised benefits to communities and businesses along the route.
Dame Meg Hillier MP, chair of the committee, said: “HS2 is already one of the single most expensive taxpayerfunded programmes in the UK but there’s actually no clear end in sight in terms of the final cost, or even the final route.
“The development of Euston is a real challenge that must be resolved swiftly now.”
Phase one, from London to the West Midlands, is planned to finish in 2025.
Euston station is a key part but MPs say crucial decisions have yet to be made over its design.
The Government still needs to decide how Phase 2b — the northern section of the route — will integrate with other parts of the railway and transport system.
HS2 Ltd said: “HS2 Phases One and 2a have received parliamentary approval and have very clear cost ranges.”
The DFT has been contacted for a comment.