The Campaign to Protect Rural England (CPRE) said a decision not to "call in" the planned Weymouth Relief Road could threaten rare habitats.

But the government said it would not interfere in the planning process.

The 3.75km (2.3m) stretch of carriageway is aimed at tackling traffic jams along the A354.

This is a shocking decision Tom Oliver

Dorset County Council confirmed at the weekend that the Government Office for the South West would not be calling for a public inquiry.

Compulsory purchase orders will now be made for the required land.

Protesters say the planned road will wipe out part of an ancient woodland and generate a significant quantity of carbon dioxide in its first year of use alone.

Tom Oliver, CPRE's head of rural policy, said: "This is a shocking decision which shows a breathtaking disregard for the government's own stated aim to protect nationally protected landscapes and wildlife sites.

'Environmental destruction'

"It is difficult to see how any landscape, however special, or any habitat, however precious, is safe when the government refuses even to acknowledge that a serious conflict exists between a new road like this and the treasured sites that lie in its path."

Angus Campbell, Dorset County Council leader, said in a statement that because the area would be hosting the Olympic Games sailing events "it is more important than ever" that the road is built.

But CPRE said the Olympics should not be "used to justify environmental destruction and increased carbon emissions on this scale".