The new high-speed rail link proposed to run between London and Birmingham was branded a "white elephant" today.
Pressure group Taxpayers' Alliance said the planned scheme, known as HS2, would cost £17 billion and yet would only benefit a minority of rail passengers.
The 200mph link would neither produce a financial return nor cut greenhouse gas emissions, according to a report produced for the group by rail expert Chris Stokes.
They claimed it was an inappropriate move in difficult financial conditions.
Director Matthew Sinclair said: "Politicians should focus on making commuter journeys more convenient and affordable, not a flashy new train set that will be a huge white elephant."
Mr Stokes, a former executive director of the Strategic Rail Authority, said the business case for the link had "not been made".
He added: "The Department for Transport have promised before that they wouldn't justify major new capital investment on the basis of overly optimistic projections for demand, but they have done exactly that in this case.
"The need for new capacity can be better served with longer and more frequent trains on the existing quick InterCity service, which wouldn't need anything like the same subsidy. HS2 should be cancelled."
Mr Sinclair added: "It is incredible that while the Government are imposing higher taxes on ordinary families, and making necessary cuts in spending on services like education, they are planning on throwing billions at a new train line that will only benefit a well-off few.
"Passengers on the new high-speed line are never expected to pay enough to cover the project's costs in fares and it will depend on massive subsidy at the expense of millions who never use the line.
"This just can't be a priority with the massive scale of the fiscal crisis and huge pressure on family budgets."
An Association of Train Operating Companies spokesman said: "High-speed rail (HSR) forms an important part of ensuring that the UK can meet the transport challenges the country will face in the future.
"Demand for rail travel is expected to double in the coming decades and inter-city routes are beginning to fill up as more and more people choose to travel by train.
"A new high-speed line, alongside sustained investment in the existing network, is key if we are to meet the significant growth in passenger numbers that is expected in the years ahead."
However, Professor Stephen Glaister, director of the RAC Foundation, agreed with the report.
He said: "The mood is swinging away from high-speed rail as the facts rather than the rhetoric are finally being heard.
"Earlier this week the Labour Party said it is reviewing its transport policy and could give no commitment to HSR.
"In austere times one must really question whether it is wise to spend £17 billion to allow the wealthy to travel quicker between Birmingham and London, whilst cutting many transport services with greater and more widespread public benefits.
"Increasingly, the evidence, as underlined by this report, shows it's not."
A Department for Transport spokesman disagreed with the findings of the report, saying the link would generate "massive economic benefits".
He said: "Building a high speed rail network will allow us to grasp a once-in-a-generation opportunity to reshape Britain's economic geography and ensure that every part of the country contributes to and benefits from future growth and prosperity.
"This will not be 'a railway for the rich'. We have modelled on the basis that the line will have the same fares structure as the existing railway. The line will be broadly carbon neutral, but allow a huge increase in travel and generate massive economic benefits with it.
"Intercity rail travel has risen sharply in recent years. Already some of our key rail arteries are close to capacity, so doing nothing is simply not an option.
"To duck this issue now would consign Britain to steadily deteriorating travel times and conditions between our major cities."
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