A New South Wales (NSW) police officer has been charged with allegedly assaulting a protester at a pro-Palestinian demonstration in Sydney earlier this year.

Hannah Thomas, a former Greens party candidate, alleges she was punched in the face by an officer during a June protest in Belmore. Her injuries required surgery.

The protest was held outside SEC Plating, which demonstrators say supplies weapons parts to the Israel Defense Forces (IDF). The company has denied the claims.

NSW Police said the employment of the senior constable, 33, was under review and a critical incident investigation - triggered when an officer is involved in an event resulting in death or serious injury - was ongoing.

The police officer, charged with assault occasioning actual bodily harm, is due to appear in court next month.