The decision means all local authorities will now be legally obliged to tell C20 of all applications for listed-building consent involving the demolition - or partial demolition - of listed buildings.
The society has responded to the news with joy, as it will no longer have to rely on members and supporters to tip it off when buildings are threatened.
Chairman Gavin Stamp said he was delighted that the society's work was now being recognised.
'It is cheering that an anomalous situation has been rectified and that we now have the same official status as our senior colleagues, the Society for the Protection of Ancient Buildings (SPAB), the Georgian Group and the Victorian Society,' he said.
'This recognition also indicates how important the architectural legacy of C20 has become and how much casework we now have to deal with,' Stamp added.