The National Library of Wales at Aberystwyth is resisting any attempt to change its status and make it part of the Welsh assembly government.
The National Library was set up by Royal Charter in 1907
Library chiefs have warned Culture Minister Alun Pugh any attempts to bring it under governmental control would threaten its effectiveness.
They also warned that the library's charitable status could be eroded or destroyed by any change.
The concerns were made in a submission sent to Mr Pugh and seen by BBC Wales.
The warning adds that any change would be costly, time consuming, and could affect the professionalism of its staff.
It also says any move would probably need parliamentary legislation.
The library, set up by Royal Charter in 1907, has the right to receive a free copy of every book published in the United Kingdom.
It has thousands of manuscripts and archives, pictures and photographs, maps, sound recordings and moving images, available for consultation.
There was nobody from the Assembly Government or the National Library to make a comment.
A number of cultural bodies are worried about the situation.
"The library is a statutory body, an organisation with a good record of looking after our literary and archival treasures," said the chair of the Welsh Academy, author Harri Pritchard Jones.
"The assembly does not have a track record.
"But more importantly, I am against totalitarianism where the government takes care of things they know nothing about.