Conservationists are continuing to fight an Oxford University plan for a £29m book depository which could alter the view of the city's dreaming spires.

Last year, city councillors turned down the project, prompting the university to appeal, and a planning inquiry started at the Town Hall on Tuesday. The city council refused consent on the grounds that the building at Osney Mead, in West Oxford, would damage the city's historic skyline.

It also objected on the grounds that it would not provide enough renewable energy, and that the university had not provided sufficient reassurance regarding flood risk.

The council's case is being backed by the Oxford Preservation Trust. On Thursday, the trust called an expert witness to put the case for protection of views of the city's skyline.

Historic landscape expert Julian Munby told the inquiry: "The proposed library building would have a major effect on the most significant of the historic views of this university city, which has outstanding universal value.

"It is an inappropriate and unsustainable way to conserve the historic collections of the university library."

The inquiry heard that Oxford's famous skyline had inspired numerous artists over the centuries, including JMW Turner, who painted the city in the 1800s. Mr Munby added: "Oxford has always attracted artists, and views of the city's skyline have always been a notable component of their output, from the 16th to the 20th century. The western views remain the least encumbered and most accessible of the historic centre."

Earlier this week, the university told the inquiry that the depository was crucial to the long-term future of the Bodleian Library, in Broad Street - and the whole library service. Its case will be set out in detail next week.

If the depository gets the go-ahead, it will hold up to eight million books. Library staff say efforts to update the Bodleian will have to be put on hold if the depository does not get the go-ahead.

Earlier this year, Julian Blackwell, president of Oxford publishing and bookselling firm Blackwell's, donated £5m towards the redevelopment of the New Bodleian.

The Bodleian's collection include the papers of six British prime ministers, a Gutenberg Bible, Lord Of The Rings author JRR Tolkien's papers a quarter of the original copies of the Magna Carta, and more than 10,000 medieval manuscripts