SCOTLAND'S castles and ancient monuments face a £65 million repair bill over the coming decade just to keep them in a "satisfactory condition", a new report has warned.

Analysis by Historic Environment Scotland (HES) has warned that the effects of climate change and the venerable age of many of the properties means that more than half of them are now at risk.

It estimates that tens of millions will be needed to keep landmarks such as Edinburgh and Stirling castles and the neolithic world-famous village of Skara Brae on Orkney from crumbling.

Adverse weather caused by climate change and coastal erosion have been highlighted as the main dangers facing the country's wealth of historic sites, and tens of millions will be needed to ensure they are preserved during the next decade.

HES also estimate that an extra £2.1 million needed each year after 2027 to sustain the buildings and heritage sites for future generations.

The progress report on the conservation and management of historic sites said that more than half of 352 managed by HES are at risk from climate change, while almost 90 per cent were found to be exposed to "damaging" environmental effects.

Taking into account factors such as the presence of site staff and conservation teams, 53 per cent were thought to remain "at risk" from hazards such as flooding and erosion, with 28 sites classified as very high risk and 160 as high risk.

HES, which manages properties on behalf of Scottish ministers, said climate change and extreme weather were putting "additional stresses" on historic buildings and "acting as a multiplier" to their natural deterioration.

Work to mitigate these effects has already begun at some sites, including rock containment at Edinburgh Castle and coastal protection works at Blackness Castle in West Lothian.

Scotland's historic sites attract hundreds of thousands of tourists each year and are worth millions to the economy.

HES warned of "resource challenges" as it estimated the multi-million pound investment which will be needed over the next ten years to ensure the "satisfactory condition" of its properties.

Culture Secretary Fiona Hyslop, who commissioned the report, confirmed Scottish Government funding of £6.6 million to support conservation work, repairs and visitor facilities at sites including Doune, Stirling and Edinburgh castles.

She said: "From Doune Castle to Skara Brae, these iconic buildings and monuments represent more than 6,000 years of Scottish history and include a number of internationally-significant sites that attract thousands of visitors every year.

"By their nature, they are often difficult to care for and require specialist expertise to repair.

"Adding to this challenge, it is well understood that climate change is speeding up the natural process of decay at heritage sites across the world.

"Historic Environment Scotland's new conservation study gives us a detailed understanding of the impact on our own heritage sites and tells us what is required to protect and preserve them for the future.

"The funding I have announced today underlines the Scottish Government's commitment to protecting and promoting our rich history and heritage, and will enable conservation work to begin at several of our treasured heritage sites."

Dr David Mitchell, HES director of conservation, said the report would "provide a basis for investment decisions over the next decade and determine how we will manage over 300 of Scotland's most cherished places and associated collections for future generations."