Former Liberal Party powerbroker and current Transport and Main Roads director-general Michael Caltabiano has been referred to Parliament's ethics committee and could face criminal charges over comments made during a budget estimates hearing.

Speaker Fiona Simpson's office has confirmed Mr Caltabiano was referred after comments he made at a budget estimates committee meeting last week, in which he said he had no previous professional relationship with Ben Gommers, who is now employed as Mr Caltabiano's departmental liaison officer.

Transport and Main Roads Director-General Michael Caltabiano. Credit:Robert Rough

However, Mr Caltabiano's involvement in Entree Vous, a lobbying firm part-owned by Mr Gommers, had since come to light.

Mr Gommers is the son of Art Minister Ros Bates.