The cost of the HS2 rail project which will travel through parts of Buckinghamshire and Northamptonshire could reach at least £80bn, almost double the current estimate.
The study by the Institute for Economic Affairs called for the project to be scrapped according to the Sunday Telegraph.
In the report, to be published tomorrow, the IEA says the cost of the scheme has been vastly underestimated, and argues that the £80billion price tag could deliver £320billion of value if spent on road and other rail and transport projects.
Campaigners are also warn that more than half a million people will have their lives affected by the project's construction.
HS2 has been launched to provide a 250mph rail link between London and Birmingham from 2026.
The report suggested that the government's £42.6bn estimate would spiral because of a variety of factors, including changes to routes and extra tunnelling to placate opposition from campaigners; new stations, grants for regeneration and compensation for towns and cities bypassed by the new line.
An HS2 spokesman told the paper: "We have considered all construction access routes as part of the development of the draft Environmental Statement... The consultation was open to all members of the public to respond.. We have sought to provide construction access with minimal disruption.
In developing the subsequent formal Environmental Statement, we will be considering how we can further reduce any adverse impacts. HS2 Ltd is still developing transport routes for the construction of the line, accordingly it is not possible to definitively say how the road network will be used."
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Dry for much of the day. Some rain this evening.