A group of relatives of the leaders of the 1916 Rising said they could take legal action to stop works at Moore Street in Dublin from going ahead.
The Save Moore Street Campaign says the entire Moore Street terrace needs to be saved, and not just the four units which are declared a National Monument.
The group says it will go to court at the end of the month unless the rest of the terrace is also saved.
Somebody in authority must protect the national interest," said James Connolly-Heron, great grandson of James Connolly.
"It's time for intervention from the State , [which] has washed its hands since 2007, and allowed a national monument – the foundation stone of this Republic – to fall into disrepair and disgraceful decay.
"It's time for the State to intervene and reverse that appalling vista."