Evidence ... authorities burn marijuana from Schapelle Corby's boogie board. Picture: Lukman S Bintoro

But he said the Government was not hiding anything that could have helped Corby, who travelled from Brisbane to Sydney and then to Bali where she was arrested in October 2004 after authorities found 4kg of cannabis in her bodyboard bag.

Despite claiming Australian baggage handlers were responsible for stashing the drugs in the bag, Corby was convicted by a Bali court and given a 20-year jail term.

Her mother Rosleigh Rose today maintained her daughter's innocence and said the Federal Government was not telling the truth.

"They have used my daughter to cover their own a***s and it's all going to blow up in their faces," Ms Rose said. "She has to come home because she is innocent."

Senator Ellison said the camera coverage areas overlapped and at no stage was there any area not under surveillance.

"On October 8, 2004 when Schapelle Corby travelled through Sydney airport we had no problems with our cameras," he said.

"The two isolated incidents in relation to the positioning of these cameras related to other times and in any event there were other cameras surveilling the same area."

Senator Ellison said it was believed at least there may have been deliberate tampering with one of the cameras.

"In one instance we believe there may have been some human involvement and that has been the subject of a Customs inquiry and investigation," he said.

"We don't have sufficient evidence in relation to who may have been responsible."

Senator Ellison said he was advised there were a number of technical reasons requiring cameras to need refocusing.

"Reports that these cameras were damaged are false," he said.

"There have been reports they were smashed. That is indicative of the beat-up and scare mongering that's going on."

Labor has attacked the Government for what it has described as a major security blunder.

ALP backbencher John Murphy said tampering with the security cameras meant heroin could have been placed in an innocent passenger's baggage and there would be no record.

One of Corby's former lawyers, Robin Tampoe, said the Government should have offered the information earlier.

"These are all things that they knew," he said on ABC radio. "They were all things we were screaming and begging for in terms of our defence of Schapelle Corby but it was denied to us.

"As these things seem to do, they bubble to the surface but they bubble up too late.

"Her appeal process has been exhausted and from where I sit, I'm just very angry about it."

The revelations could also have implications for Operation Mocha, in which a syndicate allegedly ran $30 million in cocaine through the airport with the help of corrupt baggage handlers.

The cameras had been used to monitor the behaviour of baggage handlers as they sifted through luggage behind the airport's check-in.

The revelations come after an internal customs report in September 2004 that revealed large-scale corruption among baggage handlers and other airport staff.

"Intelligence from other law enforcement agencies suggests some Asian-recruited Qantas crew may be involved in narcotics," the report found.

The report also revealed baggage handlers would divert bags containing drugs from incoming international flights to domestic carousels so they would not be checked.

New South Wales Police Minister Carl Scully said claims about the cameras were not new and Qantas, the Federal Government and Sydney Airport Corporation had made efforts over the past two years to boost security at the airport.

"Well, that's been known for a while, both anecdotally and more than that, that cameras had been upset, dislodged, damaged, defaced as a means of preventing the observation of baggage handlers," Mr Scully said.

"I think the airport corporation, the Federal Government and Qantas have made a lot of improvements. I know they've laid cable, they've put cameras in place.

"So I'm not going to be critical of Qantas or the airport corporation or the Federal Government over this."

Sydney Airport Corporation Limited (SACL) said it was a matter for the Federal Government.

"The cameras which are referred to in that story are Customs cameras, and they're controlled by Customs, they're not controlled by Sydney Airport," a (SACL) spokesman said.

In a recent case involving corrupt airport workers, former Qantas baggage handler Raymond Camilleri was this week sentenced to one year of home detention for tipping off a cocaine dealer that police had seized his luggage.

Camilleri tipped off the dealer on February 17, 2005, once again at the same time the security cameras were found to have been disabled.

Corby was arrested at Bali's Denpasar Airport in October 2004 after authorities found four kg of cannabis in her bodyboard bag.

Despite claiming Australian baggage handlers were responsible for the cannabis being in the bag, Corby was convicted by a Bali court and given a 20 year sentence.

with The Daily Telegraph's Luke McIlveen

Video Interview with John Murphy - Schapelle Corby Case Information

Head of Qantas security Geoff Askew admitted there was a two-year gap between the initial security screening of staff and the next security check, News Ltd newspapers reported.

If staff are convicted of a crime in that period they can continue working undetected in top-security areas for up to two years unless they volunteer the information.

"That's possible and that's a flaw in the system," Mr Askew said. The revelation follows reports last week that convicted cocaine dealer Easton Barrington James had worked as a Qantas baggage handler at Sydney Airport for four years.

Mr Askew said Qantas found out about James' conviction only by way of rumour.

"We got him in and to his credit he told us what happened," he said.

"The current system is hard because unless the person comes forward and tells us we can wait two years for the government to tell us."

He called for live monitoring of all people holding aviation security ID cards, for which workers undergo ASIO, federal police and Immigration Department checks.

Mr Askew also called for police intelligence to be used in background checks, not just criminal convictions.

Schapelle Corby Case Information

NEW South Wales Police Minister Carl Scully said today he was not too concerned by claims security cameras at Sydney Airport were sabotaged.

But today Mr Scully said claims about the cameras were not new and Qantas, the Federal Government and Sydney Airport Corporation had made efforts over the past two years to boost security at the airport.

This followed the Federal Government's Wheeler report, a major investigation into aviation security.

"Well, that's been known for a while, both anecdotally and more than that, that cameras had been upset, dislodged, damaged, defaced as a means of preventing the observation of baggage handlers," Mr Scully said.

"I think the airport corporation, the federal government and Qantas have made a lot of improvements. I know they've laid cable, they've put cameras in place.

Schapelle Corby Case Information