A historic bridge across the Thames will have to be replaced by a new one on a different site, highways engineers have warned.

New Bridge, on the A415 Abingdon to Witney road near Standlake, is crumbling under the volume of heavy lorries.

Oxfordshire County Council engineers are alarmed at the speed at which the historic bridge, which dates from the 12th century, is deteriorating.

They have decided it cannot be strengthened and a new bridge must be built nearby, crossing a beautiful section of the Thames.

The bridge, five miles west of Oxford, has the pubs the Maybush and the Rose Revived at either end, with beer gardens overlooking spectacular riverside scenery.

New Bridge, a scheduled Ancient Monument, is now considered too narrow to handle the levels of traffic using the A415 to avoid the heavily congested A420, A40 and A34.

But villagers in nearby Standlake say the bridge's narrowness acts as a deterrent to heavy lorries and fear a new bridge will result in further traffic misery for their village.

They want weight restrictions imposed instead.

The county council says it is still deciding how best to realign the road to bypass the old bridge. The Local Transport Plan proposes construction of a new bridge as early as 2009.

Head of transport Steve Howell said: "We are having to monitor the bridge to make sure it is not deteriorating faster than we expect. It is an A road carrying HGVs and we have no choice but to make sure we have a safe and stable structure across the river there."

He said preliminary work had started to see how best to bypass New Bridge. It is not known whether the road would be diverted to the east or west but the sensitivity of the site means it is likely to be as close as possible to the current road.

Standlake parish and West Oxfordshire district councillor Brenda Smith said the council should impose a weight limit instead of building a new bridge.

Ms Smith said: "We have been asking for this for a long time.

"Money used for a new bridge would be better spent on improving the A40 link with the A34. This is just a short term solution, a sticking plaster. It is going to ruin the ambiance of the bridge and the Rose Revived."

Maybush landlord Brian Ward said: "It's a very attractive spot. We are still trying to get information about what is being proposed."

Standlake Parish Council has now appealed to Witney MP David Cameron to intervene.

Vice-chairman Chris Naylor said: "We are really concerned. We know what would happen a massive increase in traffic going through the village. We need some clarification about what exactly they are prop- osing."

He said the recent closure of a section of the A415 over several months showed heavy goods vehicles easily managed to find other routes.