For the third time in six months, detectives this week descended on a small area of bushland in the sprawling Royal National Park in the hope of finding any trace of Mr Leveson.

Officers returned to the site near Waterfall on Monday to make sure they had not missed anything in the fruitless searches in November and January.

Mr Leveson, then 20, was last seen leaving ARQ nightclub in Darlinghurst with his then-boyfriend Michael Atkins in September 2007.

Mr Atkins, 54, was later charged with Mr Leveson's murder but was acquitted after a trial in 2009. He has long denied having any role in Mr Leveson's death.

He faced intense questioning in the NSW Coroner's Court last year during an inquest into Mr Leveson's disappearance and after he was granted immunity, meaning his testimony could not be used against him in any future criminal proceedings.

However, that did not protect him from contempt of court or perjury charges.

In a bid to finally find Mr Leveson's body, his parents Mark and Faye consented with the NSW Attorney-General in offering Mr Atkins, who now lives in Queensland, a second olive branch.

Mr Atkins agreed to a deal under which he was granted immunity from a perjury charge if he showed investigators where Mr Leveson's body was.

The inquest took a sensational turn in November when Mr Atkins provided police information as to the possible grave site in the Royal National Park.

Mr Atkins pointed police to a leafy area off a bend in the road not far from a train station but claimed he couldn't remember exactly where he thought Mr Leveson's remains were.

Days of searching, with the help of heavy machinery, failed to find any sign of Mr Leveson.

An area further down the road was searched for a few days in January but again nothing was found. The result was devastating for Mr Leveson's parents, who have been unrelenting in their pursuit for justice.

This week's operation, expected to go on until at least Friday, is focused on the same area of bushland to make sure no stone is left unturned.

The search perimeter has been widened and a backhoe brought in.

"As part of continuing efforts to locate the remains of Matthew Leveson, police are conducting a further search in Sydney's south this week," a police spokeswoman confirmed.

"Detectives from the State Crime Command's Homicide Squad's Strike Force Bowditch commenced a co-ordinated search in the Royal National Park about 8am on Monday."

Mr Leveson said the current search was about dotting the i's and crossing the t's.

"The long-term plan is, and it has always been, that we are not going to give up," he said on Wednesday.

Mrs Leveson said she tried not to get her hopes up because in the past she came down with a thud when her son wasn't found.

She said Mr Atkins had shown no remorse and no emotion throughout the entire case.

"He said he loved Matt but if you love someone why would you go to the trouble of dumping someone in the bush and discarding them like rubbish?" she said.

The inquest is due to resume in August.