A Bronze Age stone circle, a Saxon monument and a 1930s lido are among tens of thousands of historic sites to have fallen victim to the ravages of time and vandals armed with spray paint.

Alarm at the scale of such destruction has prompted plans for the first comprehensive register of England's neglected and decaying heritage to assess the full extent of the problem. No other country in Europe has produced such a picture of its heritage.

Having focused its attention to date on Grade I and Grade II* listed sites, which make up just 8 per cent of the country's protected sites, English Heritage is now including Grade II buildings to determine how many of these are at risk as well.

The Heritage at Risk project, to begin in July, will include scheduled monuments, archaeology, historic landscapes, parks and gardens, places of worship, conservation areas, battlefields and maritime wrecks. Crumbling churches and castles will be listed alongside deteriorating libraries, swimming baths, schools, hospitals and police stations.

Such is its ambition — with more than half a million sites to explore — that the survey will take three years.

“It's a massive task,” said Simon Thurley, the chief executive of English Heritage.

“Even in its first year, our Heritage at Risk project will constitute the most detailed picture ever gathered of the true state of the nation's heritage. Year on year we will be able to see how much of this heritage has been rescued and what is still at risk.

“What we desperately need to know is where the priorities are, where the problems are and why these things are happening. One of the things we will put in the register this year will be why so many prehistoric and medieval earthworks are at risk. We may find out that it's animal damage we've got to deal with. This will allow us to start on strategies to stop that happening.”

Such a systematic survey of heritage at risk will enable experts to prioritise the most urgent cases. Seeing the whole picture will also allow them to identify solutions that can be applied across the whole country.

Dr Thurley said: “The long barrow overgrown with brambles that you saw on your last country walk, the Civil War battlefield under threat of development, the broken war memorial in the village square or the boarded-up old mill buildings that no one seems to care about: these are all part of the rich backdrop of our lives in England.

“But our heritage is a finite resource and if we don't act, these things won't be here for our grandchildren.”

The list will include Uxbridge Lido, a Grade II listed building dating from 1935. At 67m (220ft), it is the second-longest open-air swimming pool remaining in London. Since closing in 1998 for health and safety reasons it has been severely vandalised.

The Bronze Age Birkrigg Common stone circle in Cumbria will also feature on the list because its stones have been sprayed with paint on more than one occasion.

Dr Thurley particularly lamented the demise of Devil's Dyke in East Anglia, thought to be a Saxon boundary between two kingdoms: “It's not only a fantastic piece of the heritage, but it's a wonderful recreational amenity. It has suffered from a lot of erosion and tree damage. Surely we can find a way of managing this better so it won't be worn away.”

He emphasised that Heritage at Risk was “not a name-and-shame exercise”, but an attempt to focus attention on the neediest cases.

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