County Hall has been accused of neglect after a landmark building fell into disrepair.
Buckets were put around Carnegie Library in Lynn last week to collect leaking rainwater and evidence of damp has also been found.
It has left councillor Alexandra Kemp angered at what she believes is evidence of Norfolk County Council (NCC) failing in its duty to maintain the town’s heritage.
But County Hall insists repairing the building “is a priority”.
Ms Kemp said: “People are very worried. They treasure the Carnegie Library but the county council are entirely out of touch.
“Why is NCC not prioritising protecting the assets they already have rather than focusing on big vanity projects?
“Is this the sort of neglect Lynn will suffer if the County Deal goes ahead?”
Ms Kemp fears the “Norwich-bias” of Norfolk County Council will worsen if more centralised powers are approved this December as part of the Norfolk devolution deal, leaving other areas of the county forgotten.
Norfolk County Council has said it takes seriously the need to safeguard the “heritage fabric” of the building but due to the age and its listed status, issues are “difficult to fix”.
It says it has been aware of the leak since July at times of heavy rain, which caused water to come through the lead-encased glass panes, and that it is working with specialists to understand the extent of the problem.
The 118-year-old building is to be sold off to voluntary groups as part of efforts to create a new £12.4m community centre at a former Argos store in the town – a move that has been likened to moving Norwich Castle into an old shop.
NCC has said the challenges faced to fix the building are one of the reasons why it is developing the modern library facility.
But Ms Kemp fears NCC is not being forthcoming about the full extent of repairs needed, which will leave the new owners with a hefty bill and that funds should instead be used to keep the Carnegie running for the purpose it was built.
“Spending public money to house a historic library in a concrete wreck is an unforgivable waste of taxpayers’ money,” she added.
