Police directed a 15-year-old to expose his genitals and officers illegally stripsearched at least 25 children at a Sydney music festival this year, an inquiry has heard.

Key points: The inquiry will focus on three teenaged boys who were strip searched at the Lost City Music Festival

The inquiry will focus on three teenaged boys who were strip searched at the Lost City Music Festival The inquiry heard dozens of children were strip searched without a parent or guardian present

The inquiry heard dozens of children were strip searched without a parent or guardian present An officer was accused of rubbing a young boy's buttocks during one search

NSW's Law Enforcement Conduct Commission (LECC) has begun a five-day hearing into several strip searches undertaken at the Lost City Music Festival held at Sydney Olympic Park in February.

The event was for teens aged 13-17.

WARNING: This article contains graphic content

Counsel Assisting Dr Peggy Dwyer told the hearing only five of 30 teenagers police stripsearched during the event had a parent or guardian present while the procedure was completed, despite it being required by law.

The hearings will focus on three cases of boys aged 15, 16 and 17 who were stripsearched at the music festival.

None had a parent, guardian or support person present and no drugs were found.

In one case, a 15-year-old boy known as GENC13 was stripsearched after a sniffer dog lingered near him.

In an interview with the LECC, GENC13 said a police officer then asked him to pull down his pants.

Ms Dwyer on Monday told the hearing an officer directed the boy to: "Hold your dick and lift your balls up and show me your gooch."

The commission heard the boy was separated from his older brother and placed in a security area before police searched both his wallet and phone, including his messages, without permission.

Ms Dwyer said the 15-year-old "froze" during the procedure and was now fearful of being close to police.

There were large crowds at the Lost City Festival earlier this year. ( Instagram: Goodlife Presents )

In another case, a child known as GEN15C told the LECC he was stripsearched by an officer who was not wearing gloves.

He said the officer touched his testicles and rubbed his buttocks during the search.

"At that time the male officer inserted his hands inside GEN15C's underwear, and made contact with his testicles," Ms Dwyer said.

It is further alleged that after doing so, the officer moved around behind GEN15C, placed both hands inside his shorts and ran his hands around his buttocks, in a circular motion, in an effort to find drugs.

A NSW Police superintendent who gave evidence at the hearing said two volunteers from the State Emergency Service (SES) were enlisted as independent support people to be present during some strip searches at the festival.

They were expected to be there if an underage person had declined to have a parent or guardian present.

The commissioner, the Honourable Michael Adams QC, said: "How would you assess the suitability of SES volunteers to be suitable for such a position?"

"It's not part of their normal duties to watch naked young people be searched by police," the commissioner said.