Council leaders in North Dorset have joined the battle to improve nightmare conditions on the A303 South West holiday route, one of the region's most traffic-clogged roads.

Chief executive Liz Goodall has written to the highway authority calling for the single-carriageway section between Wylye and Mere, on the Wiltshire-Dorset border, to be dualled.

This followed a unanimous decision by councillors who are concerned that the one-lane stretch simply cannot take the huge amount of heavy traffic that it is subjected to.

In December there was outrage among scores of communities in Wiltshire, Somerset and Dorset over plans to close a stretch for 14 weeks starting this month for a repair programme.

However, the Highways Agency was forced to shelve the proposed closure of a four-mile section near Mere amid widescale fears of appalling congestion in dozens of villages.

They said there would be three months of hell as a result of jams and tail-backs as up to 30,000 vehicles a day sought alternative routes.

North Dorset councillors have since passed a motion which Mrs Goodall has now outlined to Malcolm Wilkinson, performance manager of the Highways Agency's South West network.

Her letter says: "This council calls on the Highways Authority to dual carriageway the A303 trunk road between Mere and Wylye and urges Dorset County Council and Wiltshire County Council to make representations to this effect.

"The A303 needs dualling as a strategic arterial route and because of the high volumes of freight and traffic using it."

Mrs Goodall also said that the three-month repair work which had been planned for the stretch of road which runs between Willoughby Hedge to Mere should not be allowed to go ahead until the A303 had been dualled.

She said: "This will cause chaos by requiring freight (westbound) to go through 'B' roads which are not of sufficient standard to take it, nor of sufficient safety standard (no pavements, etc). The suggestion is that an appropriate stretch of dual carriageway be implemented first so that when the repairs are done, the traffic can use the new carriageway during the repair period."

The council's stance has pleased veteran Salisbury district councillor David Parker, who last month launched a campaign for the entire road to become dual carriageway.

Another stretch of the A303 – from Countess Roundabout at Amesbury to Winterbourne Stoke – also has just one lane each way.

A scheme to finally dual this section was scrapped because it formed part of the axed project to bury 2.1 km of the A303 in a tunnel out of sight of Stonehenge.

Councillor David Parker lives in Teffont just off the A303.

He said he has received a wave of support backing his calls for the road to be dualled throughout its length and that it was unbelievable that a road which bore motorway volume traffic remained single carriageway.

He said: "Public concern is growing. From Penzance to Stonehenge, communities are calling for the roads to be upgraded to meet modern needs of traffic and environment protection.

"The Government should be pressed to improve the stretches of the A303 that are proving to be death traps and traffic blighted."