NSW Police are investigating after an employee at a trouble-plagued Sydney hospital allegedly forged patients' signatures to have them admitted as private patients without their consent.

Northern Beaches Hospital's operator, Healthscope, sacked the employee, understood to be a patient liaison officer working in the emergency room, and referred the matter to police.

A Sydney hospital employee has been sacked for allegedly forging patient forms. Credit:Louie Douvis

A fellow employee who contacted The Sydney Morning Herald and The Age on the condition of anonymity alleged hospital management had offered patient liaison officers cash incentives to increase the number of "conversions" of public to private patients.

"Patient liaisons were encouraged to present the benefits of using their private insurance, and skim over or hide being public as even an option," the employee said.