Do we really need a dual carriageway here?

The Transport Secretary thinks it's just what Salisbury needs, but a secret official study suggests otherwise.

It may yet be saved - one of the loveliest views in England, Salisbury Cathedral seen across the Avon watermeadows, which is now threatened with destruction by a dual-carriageway trunk road.

A secret Government survey has thrown into doubt the future of the proposed A36 Salisbury bypass, one of the country's most controversial roadbuilding projects.

Statistics gathered by the Department of Transport show that the proposed road would serve mainly to relieve local, rather than through, traffic.

That could undermine the case for the road which, like the Newbury bypass, has provoked a bitter local dispute between those who believe they will benefit from it and those who say it will destroy irreplaceable landscapes and wildlife sites.

The new evidence comes at a particularly sensitive moment in the lengthy planning process, which involved a year-long public inquiry during 1993 and 1994. The Department of Transport is now backing plans to proceed with the road; the Department of the Environment is resisting.

Sir George Young, the Secretary of State for Transport, wants to proceed with the plan by issuing an instruction that he is "minded to" approve the project subject to several detailed reservations being answered. John Gummer, the Secretary of State for the Environment, is digging in and proposing possible deviations to the route although he is said to be"under tremendous pressure" to give way.

The Salisbury bypass has been the subject of one of the longest and most expensive planning inquiries in recent history, with costs estimated at pounds 1m. The inspector took 18 months to produce his report which was sent to the Department of Transport last October and is believed to have backed approval of the project provided some reservations are satisfied.

But the Department of Transport's origins-and-destinations survey, which analyses the 50,000 daily traffic movements on the A36 into Salisbury, shows that only 3,000 go into the town centre, then leave via the A36. That means that 94 per cent of the journeys on the road aremade by local traffic.

The Department of Transport funds big bypasses nationally, partly on the basis that they ease travel between big centres of population (in this case Bath/ Bristol/South Wales and Southampton/Portsmouth/the South) and enhance the national road network.

Anti-roads campaigners argue that in many cases roadbuilding can increase traffic rather than reduce it by making a series of new journeys practical. Proponents of the scheme insist it would reduce traffic originating in several points from Salisbury's historic centre.

In the run-up to a general election, an outcry of the type that accompanied the Newbury bypass could dent a green image carefully cultivated by Mr Gummer.

Many in government have drawn a parallel with Newbury where outside protesters were pitched against those local voters who are demanding measures to relieve urban congestion.

However, the proposed Salisbury bypass has powerful backers, including the local Conservative MP and former roads minister Robert Key, whose prospects of returning in the next general election could be affected by the Government's decision.

A source said: "Robert is a former minister with nothing to lose. He would probably get the support of some colleagues. The Government has a majority of one. I rest my case."

Mr Key, who claims the backing of Salisbury and Wiltshire councils, is threatening to refer the matter to the Parliamentary ombudsman if there are further delays.

He argues that Salisbury and District Chamber of Commerce can show that business has suffered as a result of continuing congestion.

The MP conducted a survey over the spring recess in which 460 of those who replied were in favour and only 45 against. He said: "I am optimistic that the right decision will be reached. If we do not get a decision very soon I would be obliged to go to the ombudsman."

Mr Key said that he did not know what action he would take if the decision went against him but he would be "gravely disappointed". At one stage Mr Key was responsible for bypass projects but, because of his constituency interest, withdrew from discussions on the A36.

Yet there are local voices raised strongly against the scheme, who are taking heart from news of the DoT study. "This survey confirms what we have already said, that Salisbury's traffic problems are mainly local in origin, and will be made worse rather than better by building a bypass," said Hamish Soutar, of the Stop Salisbury Bypass Campaign.

Mr Soutar, 38, the Green Party's prospective parliamentary candidate for the city, said the new road would do nothing but harm to Salisbury.

"It will destroy the landscape setting of the city, which is of unparalleled historical importance," he said. "It will destroy the flood-plain grassland watermeadows, which are of exceptional nature-conservation value, bordering the river Avon. which is probably the best chalk-stream system in the world.

"It will add to flood risks, and in our view it will actually make it very much harder to tackle Salisbury's transport needs., which should involve a strategy for transport reduction, particularly in the rush hour."

Mr Soutar added: "There is growing cross-party support in Salisbury for reopening the public inquiry."