HS2 is an expensive vanity project that must be scrapped, according to think tank The TaxPayers' Alliance (TPA).
The think tank said that the project costs are rising, likely to hit £90bn, with a timely delivery unlikely.
Jonathan Isaby, chief executive of the TaxPayers' Alliance, said: "HS2 is a wasteful vanity project which is unlikely to be completed on schedule and will cost taxpayers a fortune.
"The new Prime Minister should now be pursuing bold and imaginative policies to boost economic growth and increase productivity – and that positive approach must include scrapping HS2, which has cost taxpayers far too much already. Ministers should instead be embarking on more worthwhile infrastructure projects that will cost less and deliver far better value."
The TPA added that the business case for the project has now fallen apart, with demand for travel uncertain. Other projects, it continued, would provide greater value for money.
However, earlier this month newly-appointed transport minister Chris Grayling said that he has no plans to back away from the project.
Grayling said the project to bring high speed train travel between London and cities in the North, including Leeds, Birmingham and Sheffield, will remain on track.
But the TPA continued to say that HS2 is unlikely to help develop the economy of North England to the extent that has been suggested.
There has also been recent criticism from the National Audit Office, which said the project is facing "cost and time pressures".
However, EY disagreed, saying the project is essential for future growth.
Malcolm Bairstow, infrastructure leader at EY, said: “HS2 is essential for the future growth of the UK and will bring additional capacity and faster journeys to the rail network. By connecting London with the UK’s major cities, it will also help to unlock the economic potential of these key UK cities as well as rebalancing the economy.
“Post-Brexit, we need a vote of confidence in infrastructure projects like these if the UK is to remain competitive in a global market.”