Released on Tuesday, the 79-page document said the train line connecting Turin and Lyon would be “very negatively profitable”.
The TAV rail line, which is backed by the ruling League party but fiercely opposed by its coalition partner the Five Star Movement (M5S), will cost more than €20 billion in total and is scheduled to be completed by 2025.
While the line could bring in €1.3 billion euros from passenger rail traffic, that does little to offset future construction and management costs of €7.9 billion plus €463 million in lost revenue from motorway tolls and lost fuel taxes, the report said.
Work has already started on the biggest part of the project — a 58-kilometre-long tunnel through the Alps — with Italy, France and the European Union sharing the cost.
The tunnel would reduce travel time between Milan and Paris from almost seven hours to just over four.
Supporters of the line argue it would rid the roads of a million trucks and avert around three million tonnes of greenhouse gas emissions each year.
Opposition parties dismissed the report, saying it was tainted with bias.
Italy’s centre-left opposition Democratic Party noted that five of the six experts who drew up the report had previously shunned the project.
The sixth expert refused to sign off on the report.
The government will now make a decision based on the report.
France agreed last December to freeze new contracts until the Italian government had completed the cost-benefit analysis.
The TAV has become another topic of dispute between Italy and France, which last week recalled its ambassador as tensions simmered between the two governments over domestic policies.
Italy’s decision will also affect the European Union, which has already pumped hundreds of millions of euros into the project.
