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CANBERRA - Convicted Australian drug runner Schapelle Corby's last chance of a reduced sentence may be hit by claims from a former close friend of the family of cannabis smoking, cultivation and smuggling.

Jodie Power, who knew the Corbys from childhood, made the allegations on Channel 7's Today Tonight Show after passing two out of three polygraph tests.

But they have been vehemently denied by Corby's sister Mercedes, who intends suing the network.

Mercedes Corby described Power as malicious and mentally unstable, and her allegations as lies.

Mercedes has been Schapelle's main support in the Indonesian island of Bali since the former Gold Coast beauty student was arrested at Denpassar Airport with 4.1kg of cannabis packed in plastic and stuffed into a body board bag.

Corby is serving a 20-year term at Kerobokan Prison, and is waiting the outcome of her final appeal for a reduced sentence.

Power said that Schapelle and Mercedes were regular cannabis smokers and showed pictures of the pair using the drug.

She claimed to have seen a vacuum-sealed plastic bag identical to that containing the cannabis with which Corby was found in 2004, and that it had contained marijuana.

Power also claimed that Mercedes had at one stage asked her to travel with her to central Queensland to help water cannabis plants at her father's farm.

Corby's father Michael was convicted of a minor drug charge in the 1970s, and lived next door to a grower named Tony Lewis who was arrested after 5kg of cannabis was found on his property shortly before Corby's ill-fated trip to Bali. Lewis was convicted of commercially cultivating the drug, but Michael Corby was not charged.

Power further alleged that Mercedes Corby had previously smuggled cannabis into Bali and had asked her to take drugs to the island. "And I said 'no, I've got two kids and I would never do that'. She went on to tell me that she had taken them over before. She said that she compressed it [the packaged drugs] or made it smaller, and put it inside her."

Mercedes Corby said she was contacting her lawyers to take action against Today Tonight. She said Power had a vendetta against her and would do anything for money. "Jodi Power is mentally unstable and any one of my friends who knows her ... will attest to it. She is a liar and a cheat - far from the caring angel she makes out."

Mercedes Corby admitted to having experimented with cannabis as a teenager but said she was not a user nor a drug smuggler, she had never watered cannabis plants at her father's property - there were none - and that she had not asked Power to smuggle drugs into Bali.