OPPONENTS of plans to build a tunnel under Stonehenge are calling for "convincing evidence" to justify the project and assurances it will not do "further damage to the Word Heritage Site".

The Stonehenge Alliance responded to today's announcement that the government planned to push ahead with the tunnel by highlighting recent archaeological finds near the monument.

It says widening the A303 will cause "substantial damage" to the ancient landscape.

A statement for the group issued today said: "We expect to see convincing evidence that will justify road widening and the enormous public expenditure involved at this time of particular financial constraint and uncertainty."

The alliance said it did not advocate new road building at Stonehenge, but accepted the need to improve the "tranquillity and appearance" of the site and its setting.

Any tunnel must be "sufficiently long to avoid any further damage", it said.

"The 27 sq.km of archaeologically rich landscape surrounding the Stones is recognised to be of outstanding universal value to mankind, and its protection must be the priority."

The group highlighted "numerous discoveries" made in and around the WHS, including "important evidence" of a Mesolithic settlement at Blick Mead next to the A303.

George McDonic, chairman of the alliance, says: “The recent archaeological discoveries around Stonehenge underline the obvious importance of safeguarding the whole of this ancient landscape for future generations."

A statement from the group said: "The Alliance is campaigning against such a tunnel since it would cause substantial damage and fall well short of Government’s commitment to protection of the whole WHS under the UNESCO World Heritage Convention.

"We sincerely hope that UNESCO will press the UK Government to honour that obligation."