Australia's largest rail freight operator has defended a polarising job advertisement for "female only" positions.

The women-only jobs of diesel fitters and electricians with Aurizon in central Queensland were advertised as "targeted" positions last Friday.

Aurizon's chief Lance Hockridge is a former Diversity Champion but the company is now defending itself against discrimination claims. Credit:Glenn Hunt

The ads have sparked strong debate on social media, some labelling it as "reverse discrimination".

Aurizon said in a statement it was seeking to recruit more women to even up the company's gender imbalance. More than 80 per cent of Aurizon workers are men.