HERITAGE bosses are putting the government under intense pressure to make a decision on the controversial £193m project to divert the A303 trunk road away from Stonehenge.

It had been hoped that work on the scheme, which includes putting the A303 into a 2.1km tunnel where it passes the ancient monument, would have started this year.

But now English Heritage fears that with the public inquiry report still with the secretary of state for transport and a general election looming, the government will be distracted into delaying a decision until later in the year.

English Heritage said the delay in making a decision was also holding up its own scheme to build a £67m visitor centre off Countess Road, Amesbury, a stone's throw from the Stonehenge World Heritage site.

It is looking more and more likely that work will not start until 2006 at the earliest and an English Heritage spokeswoman said: "It's crucial we have a decision on the roads as soon as possible.

"We are losing momentum.

"We have put an enormous amount of work into the planning application for the visitor centre."

Plans for the visitor centre are currently being studied by Salisbury district council and a decision is expected some time during this summer.

But, even if the visitors' centre gets the go-ahead, work cannot start until the government gives the green light for the new road system.

The Highways Agency plans include the tunnel, a new dual carriageway between Amesbury and Winterbourne Stoke, a flyover at Countess roundabout and a bypass for Winterbourne Stoke.

The new road system will provide access to and from the new visitor centre.

When the three-month public inquiry into the road scheme ended in May 2004, planning inspector Michael Ellison said he expected to have his report on the secretary of state's desk by September.

But Alistair Darling did not receive the report until January of this year, putting a 2005 start in jeopardy.

The government has already come under pressure from the National Trust to make a decision.

The trust, which owns much of the land with the World Heritage site, has told Whitehall not to let the road project become "obscured in bureaucratic long grass".