The surprise move by the Department of Culture Media and Sport (DCMS) has torpedoed plans by the city council, the owner of the crumbling complex, to redevelop the building - a key site at the heart of Plymouth's massive regeneration proposals.
The city council wants to flatten the existing centre, with its 14-storey Modernist block and a lower 'mini-Festival of Britain' chamber, and replace it with a new mixed-use development, including a library.
After years of delays, the council had only recently appointed a developer - Rok Development - to take on the job, which would also see 1,000 staff move from the tower into a new purpose-built home.
Richard Longford, from Plymouth City Council, said: 'Obviously the decision causes us serious problems and we are very disappointed and surprised.
'We don't consider the building has the merit EH says it has. The tower has changed a lot and was not finished as intended.'
Originally designed in 1954 by H J W Stirling, but completed by a team including Alan Ballantyne and famous landscape architect Geoffrey Jellicoe, the building is almost universally disliked in the city and has been described by the Civic Society as a 'beast' and by the local economic development group as 'hugely ugly'.
Even Pevsner branded the building, which has suffered from a number of serious structural problems over the years, a 'disturbingly prominent lopsided imposition'.
Yet the listing has been warmly welcomed by the 20th Century Society, which recommended the building
to EH for protection.
A spokesman said: 'The council-chamber block is of superb detailing and features artworks of outstanding significance.
'It stands out in terms of style as well as of height and was conceived as an ambitious and optimistic civic symbol.'