The revelation came as Women's Minister Verity Firth told all public service agencies to review practices to ensure they were providing support to breastfeeding mums.
The female sergeant told her civilian employee that she was not entitled to paid breaks, and denied her access to a private room, all in violation of an official State Government policy that is ignored throughout almost all of the public service.
However, it is suspected that the woman officer may have been overcompensating to fit into a blokey culture, with experts likening aggressive women in uniform to "religious converts".
Feminist Eva Cox said the sergeant herself was probably the victim of a male-dominated culture, suggesting that she was trying so hard to fit in that she was tougher on women than her male colleagues.
"The women who get up through the system are the women who are really supportive of the system - they're like religious converts," the Daily Telegraph quoted Cox as saying.
"They're scared to behave in any way soft or feminine and it makes them harder on other women than blokes," she stated.
However, NSW Police Assistant Commissioner Mark Jenkins said that both genders were always treated equally in the Force.
"Police who rise up through the ranks of the NSW Police Force do so because they are the best people for the job. Gender is irrelevant," he said.
NSW Police is now developing a new breastfeeding policy, and is taking steps to address the employee's complaints - including a request that all the overtime she worked be reinstated.
The Public Service Association has lodged an action in the IRC seeking to enforce the Government's 12-year-old policy supporting new mums.