The final bill for the High-Speed 2 rail project could top £80bn - nearly double the current estimated cost of £42.6bn, The Institute for Economic Affairs has said.
The IEA, a politically neutral think tank, has told the BBC that changes demanded by local councils for additional infrastructure and changes to rail services will inflate the cost.
The think tank wants HS2 to be scrapped and the money spent on other transport schemes which offer, in its view, far better long term economic benefit.
HS2, which stands for High-Speed 2, is intended to allow trains to run at 250mph (400km/h) from London to Birmingham from 2026, with branches to Manchester and Leeds via Sheffield planned by 2032.
Current top speeds on fast trains in the UK are around 140mph.
Opponents of HS2 say the scheme will cause an unacceptable level of environmental damage, loss of homes and local community disruption.
HS2 Ltd, the company running the rail project and wholly owned by the Department of Transport, maintained its position that the project would deliver significant value and will be an economic asset.
Released today, the IEA’s report says that the cost of new trains would be £7.5bn.
The report says that changes to the route “to keep voters on side” were likely to add another £30bn to the current estimated cost of £42.6bn, which includes “contingency” money.
If HS2 were scrapped, the Government needs to consider other methods for connecting large economic centres in the north to London and the South East. The rationale for doing so is building constantly, as recent evidence in the disparity in regional house prices, and Lord Michael Helestine’s report, No Stone Unturned, strongly suggests that regional rebalancing is a clear route to overall economic growth in the UK.