A new study has said creating a tunnel for HS2 through the whole width of the Chilterns Area of Outstanding Natural Beauty is more viable than the current proposals.

The report, which was launched at Westminster Palace yesterday, said the proposed 24.2km tunnel would be less damaging to the environment and make greater economic sense.

Boring a tunnel the whole way across the Chilterns would cost £1.85billion, the report said, compared to the £1.45billion currently set aside - but campaigners said this was "a small price to pay to preserve this unique landscape".

The first nine km of the proposed tunnel would follow the same route as what is currently planned, with the next eight km then being dug deeper into the Chiltern hills rather than coming to the surface as is currently proposed.

The final eight km will then deviate west through the tunnel, meaning it will not be as near to Wendover as is currently planned.

Ray Payne of the Chilterns Conservation Board said at yesterday's launch the incline the currently proposed line would take to reach the surface near South Heath is 1/33 - which would make it the steepest on any railway line in the country.

Putting the line entirely in a tunnel would lessen the gradient to 1/100, which would make HS2 more economical to run, Mr Payne said.

The report said tunneling through the Chilterns would mean the government would have to pay out less in compensation to residents whose property value would be severely impacted by the work to build HS2.

Mr Payne said 1.9million cubic metres of earth would be removed during the tunneling process. He said a cement company in Rugby had been contacted, with the firm interested in using the spoil in the manufacturing process.

A 'firefighting' point allowing emergency access to the tunnel would be created near Amersham, in accordance with EU regulations.

The study was produced by Peter Brett Associates, a Cardiff-based development consultancy firm, after being commissioned by Chiltern District Council, Aylesbury Vale District Council, Buckinghamshire County Council and the Chilterns Conservation Board.

Cheryl Gillan, MP for Chesham and Amersham, said: "If HS2 is to go ahead, any government responsible for this project should provide the maximum protection for the AONB through a full tunnel. This special environment is valuable for future generations and should not be destroyed where extra tunnelling could provide a solution to its safeguarding."

Chiltern District Council leader Isobel Darby said: "HS2 would create a huge and ugly scar through parts of the AONB. Our proposal represents a massive improvement over the existing government proposed scheme and avoids the reckless damage that the rail line would cause."

And Kath Daly, Acting Chief Officer at the Chilterns Conservation Board, said: "The Chilterns Area of Outstanding Natural Beauty is one of England’s finest landscapes, subject to the highest levels of protection. We expect those responsible for designing the HS2 railway to take seriously their duty to conserve this special place. A long bored tunnel is the only acceptable mitigation. "

The proposals have been put to HS2 Ltd within the last few days.

The report can be viewed by clicking here.