Many train passengers will face slower and less-frequent services if the Government's HS2 high-speed rail scheme goes ahead, according to a report from the TaxPayers' Alliance.
Creating the London to Birmingham HS2 will mean Euston station in London "becoming a building site for seven years", the report said, and also claimed that until the second north-of-Birmingham phase of HS2 was built, there could, from 2026, actually be a 6.6% reduction in the number of seats available on the West Coast main line compared with 2012.
But the Department for Transport said the report was "nonsense" and based on speculation and said that the Government would continue to invest in existing railways.
The TaxPayers' Alliance also said that by 2033 there could be a 15% seat reduction on East Coast main line services from London to York, Darlington and Newcastle.
The report listed the towns and cities which, according to the TaxPayers' Alliance, will have "worse rail services as a result of HS2". These include Coventry, Stoke-on-Trent, Manchester, Leicester, Nottingham, Derby and Sheffield. These destinations would be "negatively hit by worse journey times, fewer seats and/or fewer trains per day", said the TaxPayers' Alliance.
It said: "The project is expected to cost over £30 billion (more than £1,000 per family) and has been justified on the basis that it will mean more seats on more trains, yet many towns along and around the route will, in fact, lose out".
TaxPayers' Alliance director Matthew Sinclair said: "High-speed rail isn't the right way of getting the capacity we need. The project is set to cost taxpayers a fortune and it is increasingly clear it will be a huge white elephant. While politicians are holding out the promise of a faster journey for a fortunate few, huge numbers of people will face slower and less-frequent services with more overcrowding. Everyone will still have to pay the hefty bill."
A Department for Transport spokesman said: "This is complete nonsense, largely based around speculation, guesswork and spurious crystal-ball gazing about our future plans for investment in the existing railways.
"The Taxpayers' Alliance are speculating wildly that all kinds of other rail projects won't go-ahead because of HS2. This is simply not the case. The Government has been quite clear that we will continue to invest in our existing railways as we plan for a high-speed network.
"The fact remains that some of our most important railways are filling up and that HS2 is a crucial part of the Government's strategy to deliver much needed extra capacity on the existing rail network."