The Public Accounts Committee (PAC) has criticised the HS2 project in its latest report of this session.
It speaks out against the scheme, calling it unrealistic and commenting on its growing costs.
Chair of the committee Margaret Hodge said: "The Department for Transport (DfT) has yet to present a convincing strategic case for HS2."
She stated the development "has not yet demonstrated that this is the best way to spend £50 billion on rail investment", adding that while the costs have grown, the potential benefits have shrunk.
Ms Hodge also thinks the timetable is tighter than the one used for High Speed 1 or the current Crossrail development, despite the larger scale of HS2.
PAC has called on the DfT to present evidence as to how HS2 represents the best option available for increasing London's capacity and upgrading connections between regional cities.
It also recommends DfT to set out how it aims to secure the resources needed to oversee a programme of HS2's size.