There is no business or environmental case - and no money - for the Government's HS2 multibillion-pound high-speed rail project linking Birmingham to London, MPs have been told.
The project, which could cost as much as £34 billion, was "a massive, massive gamble", said Stop HS2 convener Joe Rukin.
The scheme, involving a London-Birmingham new line and then links further north to Scotland, had not been properly assessed, Mr Rukin told the House of Commons Transport Committee.
Earlier, the MPs had been told by HS2 chief executive Alison Munro and by others appearing before the committee that the scheme would benefit Birmingham as well as London.
But Mr Rukin said the proposed new line, which will pass through some beautiful areas of southern England, was much more likely to benefit London more than Birmingham.
He said: "There is no business case, no environmental case and no money for HS2. The more we find out (about) the project, the worse it seems to be."
Matthew Farrow, the CBI's transport head, said his organisation supported HS2, particularly as there were concerns about overcrowding on the London to Scotland West Coast Main Line.
But Matthew Jaffa, deputy head of policy at the Federation of Small Businesses, said that small firms were not putting HS2 at the top of their priority list, preferring to see investment in roads rather than rail.
Stephen Joseph, chief executive of the Campaign for Better Transport, told MPs that there was a danger of "big projectitis" taking over in transport at the expense of smaller schemes.