Exhaust fumes from the growing number of buses stopping outside Oxford's Ashmolean Museum could damage its priceless paintings, it has been claimed.

Museum staff are also concerned that potential visitors are being put off seeing the historic attractions because of the temporary bus stops in Beaumont Street.

The Ashmolean

Museum director Dr Christopher Brown spoke out after the bus stops were set up outside the building's entrance, due to the closure of George Street for sewer repairs.

Dr Brown said: "Like every gallery in the world, we are concerned about levels of pollution in the air which can affect art in the museum.

"The Ashmolean is the single most-important museum outside London. Priceless exhibits can be damaged long-term by high levels of air pollution.

"We have done some monitoring. In 1999, the Oxford Transport Strategy brought more traffic along Beaumont Street and there was a 33 per cent rise in nitrogen oxide levels.

"Pictures are not deteriorating before your eyes, but a long-term build-up of nitrogen oxide is a concern.

"This gas is largely produced by idling diesel engines, so the present arrangement is not a good idea because it will increase levels.

"If there is any suggestion that the arrangement will be made permanent, then I will be writing to the council traffic departments to make my views known."

Noel Newson, county council group manager for sustainable transport, assured Dr Brown there were no plans to make Beaumont Street a permanent bus stop location.

He added: "We want to get the buses back into George Street as soon as possible. Air quality in the city centre has improved since the OTS came in.

"We have seen a reduction in pollutants in many places following a reduction in traffic.

"One of the objectives of the OTS was to reduce the damage caused to the outside fabric and stonework of buildings resulting from exhaust emissions.

"The George Street works are expected to be finished by July to make way for the start of Cornmarket Street improve- ments.

"Some bus passengers have complained that they are now having to walk too far to the bus stops, but generally we think the George Street closure scheme has worked remarkably well."

There are also plans for a stopping-off point for tourist coaches outside the museum, which could take place later this year.

One already exists on the other side of the road outside the Playhouse Theatre.