Hundreds of casualty patients in Oxfordshire are waiting longer than the Government's target time for treatment.

Since the beginning of the year, managers at the John Radcliffe Hospital, in Headington, and The Horton, Banbury, have managed to wipe out extra long trolley waits of more than 12 hours.

But they have been unsuccessful in enforcing a new objective, introduced in April, specifying that at least 90 per cent of patients must be seen within four hours.

Managers at the Oxford Radcliffe Hospitals NHS Trust, which oversees both hospitals, as well as Oxford's Churchill Hospital and Radcliffe Infirmary, said the problem was caused by bed shortages in other wards.

They said about 200 people, who no longer need their care, are taking up beds because they cannot leave until appropriate care is found for them elsewhere.

If they were all discharged, the trust could not only solve long A&E waits, but also clear a backlog of patients waiting for operations.

According to recent figures released by Thames Valley Health Authority, responsible for health in Oxfordshire, Berkshire and Buckinghamshire, the ORH has failed to meet the four-hour-or-less wait target since it came into effect.

About 500 county patients since March have waited between four and 12 hours for treatment.

ORH patient access director Jan Elliott said more than 90 per cent of patients with minor complaints were dealt with in less than four hours.

Ms Elliott said: "We just don't have beds readily available in the main hospital because we're running at such a high occupancy rate.

"This is not just an A&E problem, but across the system. We have 200 patients who have been at our hospitals for greater than 30 days, even though only a minority of these still need our care.

"If they were all discharged we would be able to solve our problems in A&E and get rid of a back log of people waiting for surgery." Many of the delayed discharges are waiting for a nursing home bed or home care organised by Oxfordshire Social Services.

A spokesman said: "Providing clients with the best possible standard of care is our priority and due to this occasionally it can take slightly longer than we would like to make sure that the most appropriate residential home place or care package, taking into account all of our client's needs, is in place."