The eight-mile bypass, which cost �100m and took 34 months to complete, opened in November 1998 after one of the UK's largest anti-road protests in which more than 1,000 people were arrested.

Swampy: Celebrity status

Ironically, the closure will re-route traffic back through Newbury. The road was meant to relieve serious jams through the Berkshire town which is close to major motorway and A-road routes to London, the West Country and the Midlands.

The Automobile Association demanded an "urgent, in-depth inquiry to establish what has gone wrong".

Bert Morris, AA public policy manager, said: "The bypass took decades to be given the go-ahead and years to build. Yet it has only taken a few months for it to go wrong."

Contractors Costain Civil Engineering will foot a �2.5m bill to rip up and replace the road's damaged porous asphalt surface.

The south-bound carriageway will be closed for one month from 1 September then the north-bound carriageway will be closed for a further month.

Controversy dogged the road both before and after its opening.

Environmental campaigners set up 29 camps and built treehouses and tunnels in an effort to halt the operation.

The protest made a celebrity out of eco-warrior Swampy and added millions to construction costs.

The eight-mile road has problems with asphalt

When it opened amid further protests last November, motorists soon complained that the bypass's access roads were dangerous. There were even reports of crater-like potholes opening in its surface.

The project director for the Highways Agency, Steve Rowsell, said about 15,000 extra vehicles would be forced to re-route through Newbury.

He added: "Although the road remains safe and the stone loss is not severe, it is clear that the surface will not last its intended lifespan."

He said work had been timed to start after the holiday period but before winter.

But West Berkshire Council said it was "extremely concerned" that repairs were needed so soon.

Chief executive Stella Manzie said: "Ultimately there will be no compensation for the disruption and inconvenience which will be caused not just to the residents and businesses of West Berkshire, but travellers nationally and internationally too."