It says parks, libraries, town halls and swimming pools are among properties being sold, often to private developers to build luxury flats.
The charity warns that cash-strapped councils are making up for budget shortfalls by selling off assets which are vital community hubs for both young and old.
It contacted all 353 local authorities in England and found a “consistently high” number of public buildings being sold year on year from 2012 to 2016.
Tony Armstrong is the charity’s chief executive and told Sky News it wants to see more of these spaces transferred to community ownership:
“When local authorities sell land and properties that we all own they’re lost forever and very few public authorities will be able to buy them back so once they’re gone they’re gone,” he said.
“More than 4,000 pieces of land and buildings are being sold of every year by local authorities and we’re not going to get these back unless we start thinking about community uses.
Community ownership is a way of keeping these buildings and land in our hands in communal hands.”
The report – called The Great British Sell Off – also found 41% of councils had no plan or strategy in place to support community ownership.
Up and down the country there are examples of public buildings under threat.
In Weybridge, Surrey, more than 15,000 people signed an online petition to save the local registry office from being sold and turned into luxury flats.
The building was built in 1911 in the Arts and Crafts style and is one of the only buildings of its type left in the area.
Following the petition, Surrey County Council told Sky News that although it has to “make sure our assets give the best value for money”, there is “no current plan” to dispose of the registry office.
Bramley Baths in Leeds was also facing closure, but a campaign by local residents saw them take over management of the centre.
It came as much relief to 83-year-old Cedric Smyth Ash who swims there five times a week:
“I know people in the pool – they’re friends now. We all know each other. It’s good. So we’d lose that and we’d have to start all over again.”
The Local Government Association says councils take their responsibilities to maintain public buildings and the public spaces in their care extremely seriously, but admit it is difficult.
Cllr Richard Watts, chair of the Local Government Association’s Resources Board, said: “With local government facing an overall funding gap in excess of £5bn a year by 2020, councils face difficult decisions about how best to use their resources to support local services, day-to-day activities and to protect public assets, such as buildings.
“Local councillors, elected by local people, understand the deep connection communities have with their public spaces and buildings.”
In response to the report, the Ministry of Housing, Communities and Local Government said:
“Councils will have £90.7bn to spend on local services over the next two years. They are responsible for managing their own finances and making the right decisions for the communities they serve.
“All local authorities must properly consider the risks and opportunities before making commercial decisions.”