A government commissioned report doubting the environmental credentials of a high speed rail link connecting the Midlands to Scotland and London should spark a public debate, train operators have claimed.

A study by consultants Booz Hamilton Allen has thrown the environmental argument for high speed rail wide open after it found that building a new track between London and Manchester would generate more carbon than the line would save over 60 years.

Transport secretary Lord Adonis has made the demise of domestic travel an explicit target for the government’s proposed High Speed Two line from London to Glasgow, scheduled for 2020.

But the report, Estimated Carbon Impact of a New North-South Line, has contradicted government claims that it could save huge amounts of carbon compared to short-haul flights.

The report said: “There is no potential carbon benefit in building a new line on the London to Manchester route over the 60-year appraisal period.

“In essence the additional carbon emitted by building and operating a new rail route is larger than the entire quantity of carbon emitted by the air services.”

But it said that if the line was extended as far as Glasgow then there would be a net carbon saving, assuming the railways captured at least 62 per cent of the market.

Virgin Trains, which has thrown its hat into the ring as a potential operator of the service, possibly as far as mainland Europe, said it would be confident of hitting the target.

A spokesman said: “I think we would be very confident of hitting the 62 percent marker.

“You just have to look at what has happened with the London to Manchester line where we totally destroyed the domestic flights market.

“We have about 75 per cent of the market there, with a limited number of short-haul flights between London and Manchester and none between London and Liverpool. And that is without the high speed element.”

The report also questioned the environmental impact of any proposed timetable.

It said that if the number of high speed trains between London and Scotland doubled from four to eight an hour, then the train operators would have to secure up to 85 percent of the market.

Virgin Trains said it was confident they could reach that target as well but said that it was up to the government to make these important decisions.

The spokesman added: “Reports like these should spark a debate about the future of rail travel in our country.

“In the end the government must look at where the passenger demands will be the greatest on this line.”

The capital cost of a hybrid line with new high speed tracks is priced at £39?billion.

In Birmingham the line could pass through either Birmingham International Station, New Street Station, or both.

Birmingham International Airport has already claimed that creating an “international hub” with access to a top class travel network would best benefit the region.

A spokesman for the airport said: “What is important here is that all transport modes are clear and honest about what footprint they may create.”