A prolific building certifier is fighting to save his career after allegations he allowed people to move into two Sydney apartment towers while they were "still a building site".

Valerio "Vic" Lilli is challenging the Building Professionals Board's decision to reprimand him and strip him of his accreditation for five years for signing off on the "Atmosphere" buildings at Castle Hill.

The Atmosphere towers at Castle Hill. A private certifier has been accused of allowing residents to move in while they were still a building site.

Developer Toplace was behind the $86 million project, which has seen the construction of 378 apartments spread across two towers neighbouring Castle Towers shopping centre.

Toplace is headed by colourful property developer Jean Nassif, who became an internet sensation over a video in which he is heard to say, "Congratulations Ms Nassif. You like?" as he gifts his wife a yellow Lamborghini. Toplace and Mr Nassif are not accused of any wrongdoing.