The early 19th century grade II building in Great Cornbow has stood empty since council staff moved out in March.
Now community activist John Young wants to galvanise support for a fight to save at least the wood-panelled parlour.
He said: “It’s part of Halesowen’s heritage and it should be preserved for future generations.
“We’ve already lost so much in Halesowen – the magistrates’ Court, fire station, hospital - which is very strange for a place with a 60,000 to 70,000 population.”
Mr Young has persuaded the council to open the building at 10am for an hour on Monday June 30 for interested individuals and organisations to look round with him.
Mr Young said: “There are a lot of listed features in the building which I think will mean the council will have great difficulty in selling it.”
A council spokesman said although the building was “surplus to requirements” there were no plans to sell it as yet as officers had only just begun to look at possible options.
But Mr Young said officers had indicated they would try to sell it and he had initially been told he could not look round it unless he wanted to buy it.
He said: “If it is sold, I think there should be a condition that the mayor’s parlour should be retained for community use.”
The upper two storeys have been unsafe for use for some time and there are issues around disabled access and toilets in blocking off the parlour from the rest of the building.
However, Mr Young believes the problems are not insurmountable and he plans to raise the issue at next Tuesday’s Halesowen North and South Neighbourhood Forum.
Halesowen South councillor David Vickers agreed the parlour should be saved as part of the town’s heritage.
He added: “To leave it as it is would be a crime, we need to do something with the building, but I’m not sure what would be possible.
“If anyone has any ideas I’d be pleased if they’d let me know.”
The council spokesman said 41 staff from the adult community and housing services were relocated from the council house to offices in Mary Stevens Park, Stourbridge, because they were more suitable.
Anyone wishing to join Mr Young on the tour of the building should contract him in on 0121 585 6771.