Schapelle Corby's imprisonment has coloured perceptions of Indonesia.

Jailed ... Schapelle Corby. Photo: Getty Images

Schapelle Corby's mother has welcomed an investigation into an alleged drug smuggling racket at Sydney Airport, saying she has always suspected corrupt customs officers planted drugs on her daughter.

Eight people, including a customs officer and quarantine inspections officer, have been charged following a two-year investigation into corruption within the Australian Customs and Border Protection Service.

Customs officers helped drug mules smuggle illicit substances from overseas, authorities allege, and then escorted them past the normal checkpoints at Sydney Airport.

Schapelle Corby's mother, Rosleigh Rose, says she was not surprised to learn of the alleged racket, saying she has always suspected customs officers were responsible for her daughter's arrest in 2004.

"I just thought it's about time someone's doing a deeper investigation," Ms Rose told the Seven Network on Thursday.

"We've always asked for it."

Corby, who was arrested attempting to smuggle 4.1kg of marijuana into Bali in a bodyboard bag, has always denied owning the drugs, claiming she was the unwitting courier for a drug gang operating in domestic airports in Australia.

Ms Rose said the Sydney Airport allegations vindicated her family's belief that Corby was set up by corrupt customs officers.

"They were covering up corruption in the airport and they did not give a damn about Schapelle."

It comes as Corby prepares to spend another Christmas behind bars, with reports that her health is deteriorating.

She is eligible to apply for parole but is unable to do so until a recently imposed ban on parole applications is lifted at Bali's notorious Kerobokan jail.

Without parole, she is not due for release until 2017.

AAP