Historic England - formerly English Heritage - is calling on people to help track down missing works of public art.
The organisation has launched the campaign 10 years to the day since a bronze Henry Moore figure was stolen from the grounds of his former estate.
It revealed that a growing number of post-war works have been destroyed, sold, lost or stolen from public places including schools and parks.
Henry Moore's Reclining Figure was worth £3m
Historic England has compiled a list of such works for the public to view.
Missing works include one of the three figures that make up Lynn Chadwick's The Watchers, taken from Roehampton University in London, and Barbara Hepworth's Two Forms (Divided Circle), which was stolen from Dulwich Park in south London in 2011.
Chief executive of Historic England, Duncan Wilson, said: "Part of England's national collection of public artworks is disappearing before our eyes. Historic England's research is only the tip of the iceberg as it's almost impossible to trace what has happened to every piece of public art since 1945.
"We're making efforts to protect the best examples of post-war public art that still exist, and make sure that it continues to enhance the public realm.
"But we also want to raise awareness of just how vulnerable these works can be and we want the public to help us track down lost pieces."
Henry Moore's Reclining Figure that was stolen from Hertfordshire in 2005 was worth £3m but police believe it was probably melted down and sold for scrap metal for £1,500.
Others have been vandalised, including an abstract steel sculpture by Barry Flanagan in Cambridge.
Historic England believes public art is under threat because of the price of scrap metal, local authority funding gaps, pressure from redevelopment and vandalism.
In 2012, Wakefield Council removed its Henry Moore sculpture from public display and put it in secure storage because of a spate of thefts.
