The failure of state and territory governments to better regulate apartment development more than five years after a major report laid out necessary reforms means up to half of all new units built could have “serious” defects, construction lawyer Bronwyn Weir says.

Apart from NSW, where new legislation gave Building Commissioner David Chandler powers to halt completion of substandard projects, states and territories had done little to implement recommendations of the 2018 Building Confidence report she co-authored, Ms Weir said.