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."
Plans for a high speed rail link between London and Birmingham, crossing parts of Buckinghamshire and Northamptonshire, could generate billions for the economy and create thousands of jobs, according to the Government.
Today the Transport Secretary announced an HS2 growth task-force to maximise the rail scheme's economic benefits. But others say the plans are a huge waste of money.
The Court of Appeal has rejected the latest challenges to Government plans to pursue the HS2 national high-speed rail project, which is to link London with the West Midlands, the North West and Yorkshire.
Fifteen councils and many other objectors, including residents' associations along the route, had asked the appeal judges to order further assessment of the project.
The judges dismissed all grounds of challenge but gave the go-ahead for a final appeal to the Supreme Court, the highest court in the country.
A High Court judge has ruled in favour of campaigners challenging the Government's handling of HS2, the high speed rail route through the Midlands.
Although he rejected all but one of five legal challenges, Mr. Justice Ouseley said the Government's consultation process was unlawful.
HS2 Ltd argue the high-speed rail will boost the economy:
"This project is vital for the economy and for our country going forward. We need the capacity , we need to improve the connectivity between our major cities. The judgement today gives us the green light to press on with the project and deliver that for our major cities."
The government will have to reconsult on compensation for people who live along the route of the proposed HS2 after a High Court judge ruled in favour of an anti-HS2 protest group.
The HS2AA group financed the case after appealing to the community for help.
Mr. Justice Ouseley upheld the challenge to the government's proposed compensation scheme on the grounds its consultation process was so unfair as to be unlawful .
Four other challenges to the Secretary of State were rejected. Joe Rukin from HS2AA said he was happy that one of the group's claims was upheld, but that HS2 would still be a disaster for many in the Midlands.
HS2 Ltd told ITV News Central, they are delighted with the overall outcome and HS2 is now on track bringing a boost to the region's economy with a super fast link from Birmingham to London. It will cost £33bn.
The Government hailed the court's dismissal of four of the five cases against it as a "landmark victory".
Rail Minister Simon Burns said: "We have listened to the judge's comments about the property compensation consultation and, to save time and public money, we will re-consult on this aspect - but this will not delay HS2.
We remain fully committed to fairly compensating the public who are impacted by the scheme."