NSW’s new police watchdog could hire back staff from the three integrity agencies it is replacing.

The NSW Parliament has passed laws to set up the new Law Enforcement Conduct Commission (LECC), replacing the Police Integrity Commission, the Inspector of the Crime Commission and the Police and Compliance Branch of the ombudsman's office.

The LECC will be solely responsible for investigating serious police misconduct and corruption and oversee the handling of complaints as well.

The NSW Government would soon begin recruiting the LECC's chief commissioner, deputy commissioners, CEO and other senior staff.

Police Minister Troy Grant says the new body will simplify and strengthen important controls on the state's police force.

“[This will] ensure that we have a strengthened, more robust police oversight body,” Mr Grant said.

“That will give the confidence ... and the surety that police corruption and misconduct will be better monitored.”

The LECC bill passed only after amendments from Christian Democrat MP Fred Nile aimed at strengthening procedural fairness matters.

“Procedural fairness is obviously an important legal principle,” Mr Grant said.

“So the Commission needs to adhere to those principles but also have the strength to make sure that they have every resource and capability to uncover misconduct within the police force and any evidence of corruption at the same time.

But the Police Association of New South Wales (PANSW) says the new authority could simply pick up the members of the old ones.

“It is now crucial to ensure the new Law Enforcement Conduct Commission (LECC) does not replicate the mistakes of the past agencies,” Police Association president Scott Weber said.

“The LECC must begin with a new culture of professionalism and accuracy, and a respect for lawful procedures and the truth.

“This will only be achieved if staff from the Police Integrity Commission and Police Division of the Office of the Ombudsman are not employed by the LECC.

“For too long, the multi-agency system of police oversight has subjected police to multiple investigations, delayed resolution, unreliable outcomes, and unjustified damage to officers' careers and wellbeing.

“This new culture must be fostered by the creation of extensive commission policies, establishing standard procedures for the commission's use of all coercive and covert powers, and the conduct if the commission during hearings.

“Only then can police have full confidence in an impartial police oversight system that is transparent, professional and effective while providing accountability.”