One of Dublin's best-known landmarks, Liberty Hall, could be demolished within two years and a new office built on the site.
This follows a decision by the leadership of the State's largest union, Siptu, which owns the building, that demolition is its "preferred option" for redevelopment of the site.
However, the union says a final decision on what to do with the 16-storey building will only be made once a number of other considerations, such as the cost of demolition and replacement, have been taken into account.
It will also consult with the lord mayor of Dublin, city planners, union members and councillors before a decision is made.
A Siptu spokeswoman said a number of options for Liberty Hall had been outlined to its members in a pamphlet last year.
These included refitting the existing building, finding a new site in the city centre, west Dublin or the Dublin docklands, or constructing a new premises on the present site. The latter was the preferred option.
"The existing building at Liberty Hall doesn't really suit our needs anymore," the spokeswoman said. "It was decided that, yes, we do need to do something rather drastic with the building but still retain the same site.
"There is no air conditioning in the building, no proper wiring and problems with the heating . . . Even doing a refit wouldn't give us the type of building we need."
She said there remained "hoops" to go through before a final decision on the building's future could be made.
These include securing planning permission, deciding what to build in its place and assessing the financial implications.
She could not say what the total cost of such a project would be.
The 41-year-old building is one of the tallest in the Republic and is on a site associated with the labour movement since 1912.
"The site is what is dear to people's hearts. It is where the Proclamation was signed and printed in the basement," the Siptu spokeswoman said.