PRICELESS exhibits in Oxford University's Museum of Natural History are being "destroyed" by sunlight coming through its iconic glass roof.

The roof of the Grade I-listed building was painstakingly restored in 2013 at a cost of £2m, but a decision by officials not to replace a reflective film on the tiles is now causing serious problems.

Staff admit the museum is "unpleasantly warm", with temperatures as high as 44C on the hottest days posing a "significant health and safety risk".

Documents lodged with Oxford City Council warn UV radiation from the sun is also causing "rapid and irreversible damage" to specimens not in glass cases, such as stuffed animals and whale skeletons.

It emerged after one of Oxfordshire's hottest weeks in a decade, with the Met Office issuing heatwave alerts after two days of temperatures of 31C or higher on Wednesday.

The museum has lodged plans to install new protective film on the glass roof but says the problem cannot be fixed without a new ventilation system, although it would not reveal the cost for the proposals.

A spokesman told the Oxford Mail: "Visitors [last] week will have noticed the combination of heat and a glass ceiling makes the museum unpleasantly warm.

"We had already applied for planning permission to install a solar protective film to the roof, to reduce the incoming UV radiation and solar heating and add further protection to the museum’s exhibits. This will be of benefit to visitors in periods of hot weather."

He explained the museum decided not to replace the previous reflective film when the roof underwent its major restoration a few years ago because "much of its protective benefit to the exhibits is now provided by UV films covering individual cases".

But he admitted the full heating effect of the roof had not been known as there was a large amount of dirt on the old one, which masked the problem.

The natural history museum attracts more than 600,000 visitors a year to view its zoological collections, boasting more than 250,000 specimens.

If work is approved, it is hoped it could begin next spring and be completed in time for summer 2017.

According to the documents lodged with the city council, the museum has been asked to address the problem by Arts Council England.

It said a peak temperature of 44C had been recorded. The recommended maximum temperature for museum collections is 25C.

The documents added: "The extreme light and UV levels are causing rapid and irreversible damage to specimens.

"In short, they are being destroyed."

While new reflective film is expected to bring down UV radiation, the museum said it was only likely to reduce temperatures inside by 1C.

Proposals for better ventilation are being drawn up and will be lodged separately, the plans said.

A spokesman for the Arts Council said: "The conservation of the museum’s collection remains the responsibility of the organisation."

Historic England has supported the proposals for new reflective film, adding it was "the least harmful way to address the problem".