Australia Post director Michael Ronaldson has attacked Labor over its role in sparking the Cartier watches saga, telling an inquiry suggestions that Christine Holgate was ousted over secret privatisation plans are completely untrue.

The former Liberal minister and Turnbull government board appointee used a high-decibel hearing on Tuesday to hit back at Labor’s Kimberley Kitching over her role in revelations Ms Holgate spent $20,000 on luxury watches, suggesting a Senate inquiry was out to “take scalps”.