The owner of one of Oxford's most important historic sites has hit back at claims the building is endangered.

English Heritage has included Osney Abbey, which was the site of one of Europe's first Jewish martyrdoms, in its national Heritage at Risk Register.

However Tony Munsey, whose family owns the remains of the 12th century abbey, which once served as Oxford's cathedral, has labelled the register misleading, as he is working to protect the remains of the abbey.

English Heritage said the only surviving wall of the Augustinian abbey was in fair condition but it had concerns that no solution had been agreed for its future.

Mr Munsey said: "The register is misleading and everyone thinks it's misleading.

"The building is in very good condition and, even if we didn't do anything to it, it would be here for another 300 years."

"It shouldn't be called the at risk register, because some of these buildings aren't at risk."

Osney Abbey, a Grade II listed building, has been owned by the Munsey family since 1910. The abbey was made a scheduled monument in 1947.

Oxford City Council declared it should be open to visitors six days a week when it granted planning permission in 2004 for four one-bedroom flats and four three-bedroom flats in the adjacent Osney Mill, which has stood derelict since a fire in 1946.

Mr Munsey said: "It's a nightmare of red tape if you have a monument.

"Even to mend a hole, you have to write letters and get consent.

"We're looking to do it up and use it and possibly convert it into an office, but if you're going to spend money on it, it has to have an economic use."

Simon Underdown, project officer at Oxford Archaeology, which is surveying the abbey site, said: "It's misleading to put it on the register, because basically the building is sound.

"I don't think it's helpful to flag it up as at risk, because it leads people to think that it's falling down, but work is taking place here to preserve it."

Mr Underdown said the building needed work to re-plaster the front gable end, which is currently patched up and repairs or a replacement for a 19th century floor, which is in poor condition.

English Heritage ancient monuments inspector Chris Welch said: "This is a nationally-important building and an excellent survival of a monastic abbey, so it needs to be included on the register.

"It isn't gong to fall down tomorrow, but it needs repair.

"No solution has yet been finalised, so it's important."

The building is the last surviving structure of a priory founded in 1129 by Robert d'Oyly, the Norman governor of Oxford. It became an abbey in 1154.

In 1222, a young Christian deacon called Robert, who was studying Hebrew at Oxford University, was executed for heresy at the abbey after marrying a Jewish woman, changing his name to Haggai and denouncing Jesus.

It was dissolved as an abbey in 1539 and became Oxford Cathedral for four years between 1541 and 1545. It then fell into ruin and was used as a source of building materials for the city.

There are four other Oxfordshire buildings on the at risk register: Bix Old Church, a Grade II-listed overgrown roofless Norman ruin near Wallingford, Hampton Gay Manor House, a Grade II-listed late 16th century roofless ruin near Kidlington, an 18th century gothic temple in Shotover Park, near Headington, and an 18th century roofless fernhouse, archway and gateway at Mapledurham House, in south Oxfordshire.