"You first and foremost have to avoid further collapses and save it," he said in an interview with Il Messaggero newspaper published on Friday.
Some historians say Nero started the great fire that charred much of Rome in 64 AD to make room for his 300 acre Domus Aurea, or Golden House that was adorned by gold leaf and dazzling frescos.
Following his suicide in 69 AD, the complex was considered a symbol of Nero's arrogance and was buried and built over after the gold, pearls and other valuable jewels laid into its some 150 rooms were stripped.
After 18 years of restoration work it was reopened in 1999 but was repeatedly closed because of collapses due to moisture.
"The problem is the rain that seeps inside," Malnati said.
"The vaults are covered with calcium and the walls are bloated with humidity.
He said the site must be restored with parts being sealed with a solution to protect it from water damage but its vast size means an effort to secure the entire area is too ambitious.
"The place is a colander and the restoration is so delicate that it required much calm and time,'' Malnati said.