Traffic on the A34 in Oxfordshire will grind to a halt within two decades if plans for thousands of new homes across the county go ahead.

Experts at the Highways Agency predict that by 2026 the A34, between the M40 and Didcot, will become one of the most congested roads in the South East.

Planned housing growth will simply clog Oxfordshire's major transport artery - and the agency says the road will not be able to cope.

The findings are part of its submission to the South East Plan public inquiry that started last month.

The draft plan - a blueprint for housing development across the region until 2026 - includes 47,200 new homes for Oxfordshire with the focus of growth on Didcot, Bicester and Oxford.

The agency's predictions could have a significant impact on that inquiry and fuel Oxford City Council's argument that homes should be built in the city's Green Belt.

The report's findings are based on predicted traffic levels in 2026 if the proposed housing developments went ahead and no action was taken to alleviate pressure on the transport network.

The report reveals that the A34 is already operating above capacity and that Oxford, the only major hub in the region, attracts more than 22,000 car-based commuters every day.

Measures to improve the situation could include travel plans for schools and businesses to encourage sustainable transport, priority lanes for buses and car share vehicles, intelligent traffic signalling and toll charges.

But the agency has ruled out widening the A34 due to environmental constraints.

Oxfordshire County Council's cabinet member for transport, David Robertson, said he was not surprised by the predictions and said improving public transport was key to reducing traffic. He said the county would also investigate bus priority lanes and intelligent traffic signalling to reduce congestion on the A34 - but he said he was not in favour of toll roads or a congestion charge for Oxford.

Mr Robertson said: "Ultimately, you can only do so much in getting people on to public transport.

"There's no option to widen the A34 or provide alternative routes so you have to think about some way of constraining traffic.

"We have been allocated £88m (by the Regional Transport Board) in 2013/14 and that is to work with the Highways Agency to look at intelligent traffic signalling - things like bringing the speed limit down when the road gets busy, as used on the M25."

He said traffic signals that hold cars off the A34 until space is available could also be investigated. But he said toll roads could create rat-runs through villages.

He added increased parking restrictions in Oxford's city centre, combined with high parking charges, was a better policy to deter car-based commuters than a congestion charge.

The county council has backed proposals for housing growth to be focused on Bicester, Didcot and Grove and Mr Robertson said building new homes on Oxford's Green Belt was not the answer.

He said: "You can hardly call the Green Belt as being in Oxford. It's as far from Oxford as some of the villages so it won't alleviate the problems in my view."

Oxford City Council leader John Goddard said: "If you are going to have more housing then you don't want it in such a place that you will have more travel by road.

"Housing has to be put near where the jobs, schools and recreation are."