Birnbeck Pier's visitor information centre and gift shop was targeted by 'mindless vandals' Tuesday night (January 11).
For six years, Pier View has been home to the Birnbeck Regeneration Trust, a conservation group who operate from there.
No items of value were thought to have been removed from the building according to the group.
The structures owner, CNM Estates, will board up the building entrance for health and safety reasons.
A trust spokesperson told the Mercury: "We are deeply saddened by this mindless act of vandalism.
"It's very upsetting because the condition of Pier View means it is extremely unlikely that any repair will take place.
"All we will be left with now is a boarded up building - it was pleasing to the eye as you walked down the prom before this mindless act.
"We do however look forward to the future of Birnbeck's regeneration with her change in ownership, there are exciting times ahead for the town."
A spokesperson for Avon and Somerset Constabulary said: "We received a report of forced entry to a commercial building which caused significant damage to property.
"Anyone with information about this incident should contact the police on 101, quoting crime reference number 5222008625.
"Alternatively, call Crimestoppers anonymously on 0800 555111."
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