Former Labour chancellor of the exchequer Alistair Darling has strongly attacked the HS2 high-speed rail project saying its economic benefits are "highly contentious".
Mr Darling, also a former transport secretary, said HS2 "ran the risk of substantially draining the railways of money over the next 30 years".
Saying that political visions "can easily become nightmare", the former chancellor added that it seemed "foolish" to commit to a project that ruled out any other major schemes.
His comments came in The Times and follow earlier reservations about HS2 expressed by Mr Darling. Former Labour Industry Secretary Lord Mandelson has also spoken out recently against HS2.
The Government has said that the cost of HS2, whose first phase will see high-speed trains running from London to Birmingham around 2026, is around £50 billion including rolling stock.
But an Institute for Economic Affairs (IEA) report earlier this week estimated the eventual cost at £80 billion and it has been reported that the Treasury is working on a figure of £73 billion.
Mr Darling said today: "It is time to revisit the case for HS2. It runs the risk of substantially draining the railway of money vital for investment over the next 30 years.
"My experience in government also makes me suspicious of big projects that can easily run out of control. Politicians are always excited by 'visionary' schemes. One thing I have learnt is that transport, rather like banking, is at its best when it is boring. That is when it tends to work. Political visions can easily become nightmares."
Mr Darling said it was true that there were capacity problems on the route from London to the Midlands and north west England but added that there were also severe capacity problems on commuter routes particularly in the south east.
He went on: "And why high-speed trains? Certainly it's handy to cut the journey time between Birmingham and London by half an hour. But at what cost?
"The economic benefit that is claimed will come from this is highly contentious. The business case depends on an assumption that passengers aren't productive - that is, that they don't work on the train.
"That may be true on a commuter train but not on long-haul intercity services. Arguably, more work is done on the train than in the office."
Mr Darling was also critical of the decision to make Euston the London terminal for HS2, saying that the station was "already congested".
Questioning the cost of HS2, Mr Darling asked: "If you gave England's four biggest cities £10 billion each for economic development could they spend it on HS2?"
Saying road, bus and cycle schemes needed improvements as well as rail, Mr Darling added: "The next Government and the one after that will be very short of money to spend on the infrastructure that we desperately need.
"To commit ourselves to spending so much on a project that rules out any other major schemes seems foolish. And the costs are not yet nailed down.
"The facts have changed. The case for HS2 was just about stateable in 2010. I don't believe it is today."