The NSW detective who led the investigation into the disappearance of William Tyrrell has been charged with misconduct offences.

Key points: Detective Gary Jubelin is charged over allegedly recording someone without a warrant

Detective Gary Jubelin is charged over allegedly recording someone without a warrant He resigned last month and his lawyer says he will now "strongly defend" the charges

He resigned last month and his lawyer says he will now "strongly defend" the charges He led investigations into high-profile cases including the disappearance of William Tyrrell and murder of Matthew Leveson

Gary Jubelin last month announced he was quitting the police force over allegations he used his mobile phone to record someone without a warrant, and a number of staff management complaints.

A departmental investigation is now underway into other allegations of misconduct.

The 57-year-old, who also worked on the Bowraville murders and the disappearance of Matthew Leveson, strongly denies the allegations.

He will face four charges related to alleged breaches of the Surveillance Devices Act.

His supporters have labelled the charges a witch hunt.

The maximum penalty for the breaches is five years' imprisonment.

NSW Police said following a "number of complaints", the professional standards command last year commenced an investigation into Mr Jubelin's conduct during operational duties.

"Those inquiries disclosed a number of recordings allegedly made at locations in Parramatta and Kendall in New South Wales," a police statement said.

Kendall is the town on the NSW mid-north coast where William Tyrrell was last seen, playing in his grandmother's front yard.

Jubelin added to internal 'wanted list'

In a statement to the media, Mr Jubelin's lawyer said the detective would "strongly defend" the charges.

"[He] is confident that these matters will shortly be resolved in his favour," Margaret Cunneen SC said.

A source close to Mr Jubelin said he had only been performing basic duties to obtain information from a suspect.

"He doesn't even know if he has been suspended from duty," the source said.

Before announcing his resignation, the detective had been confined to desk duties while the professional standards probe took place.

He is due to finish work next month.

Gary Jubelin in Kendall as part of investigations into William Tyrrell's disappearance. ( AAP: Joel Carrett )

After joining the NSW Police Force in 1985, Mr Jubelin rose to become one of the country's leading criminal investigators.

He helped solve the brutal murder of Mengmei Leng, 25, whose naked body was dumped inside a blowhole on the NSW Central Coast, and he investigated the death of mentally ill Sydney woman Courtney Topic.

His work probing the criminal activities of Australian kidnapper, murderer and drug dealer Anthony Perish was documented in the fifth series of the popular television show Underbelly.

Victim support groups across the country were shocked by the news of his departure from the police force last month.

Mr Jubelin has previously been praised by the families of the three children murdered in Bowraville as well as the parents of Mr Leveson whose remains were found in 2017.

He was chosen to re-investigate the Bowraville murders and gathered fresh evidence which led to a second trial.

Mr Leveson's parents said they would still be looking for their son, whose body was found by police in the Royal National Park, if it were not for the work of the detective.

Mr Jubelin is due to appear at the Downing Centre Local Court on July 30.