Fake $100 notes are being passed at restaurants, pubs and shops across Melbourne as a counterfeiting ring has begun flooding the city with high-quality forged bills.
The influx of forged currency comes as the federal government considers a proposal to permanently remove the $100 note from circulation because of its popularity with organised crime syndicates, drug traffickers and tax cheats using the black economy.
In December 2016, Financial Services Minister Kelly O'Dwyer established a special task force to investigate the cash economy following a surge in the number of $100 notes in circulation detected by the Reserve Bank of Australia.
The new fake $100 bills are considered to be of a high-quality with only one major flaw - each has the same serial number: "AI 13933231".
A source familiar with the bills said they had the same feel as a the polymer notes, and included the clear window with a lyrebird.
Fairfax Media understands there may be at least two counterfeiting rings currently operating around Melbourne.
Sources say one group may be behind a cache of $2 million worth of poor-quality counterfeit $50 and $100 notes that were found amongst building rubbish at a regional recycling depot in 2016. The printed but uncut bills appeared to be left over from a failed 'test run'.
Another group linked to Middle Eastern crime figures was believed to be printing notes until late last year using an industrial property in the outer northern suburbs as a cover.
It is unknown whether this latest batch of fake $100 notes is linked to either of these operations.
Last month, two men were arrested at a Chapel Street nightclub after attempting to pass two $100 bills which were fakes. The men, claimed the notes had been withdrawn from a automatic teller machine in Ferntree Gully.
According to the latest figures from the RBA, the rate of counterfeiting of $100 bills remains low in comparison to the number of $50 fakes detected.
Around 3650 fake $100 notes were discovered in 2016, compared to more than 22,000 counterfeit $50 notes.
"Liaison with AUSTRAC (Australian Transaction Reports and Analysis Centre) and the Australian Crime Commission suggests that it is the $50 denomination – rather than the $100 – that tends to be preferred by criminal elements because of its ubiquitous use in legitimate transactions," according to a recent RBA research report.
But the number of fakes detected by the RBA is likely to represent only a fraction of the amount of counterfeit notes flowing through the economy amid a massive spike in the number of counterfeiting operations being uncovered by law enforcement agencies.
The regulator has also flagged concerns about a surge in the proportion of $100 bills circulating in the economy, which has doubled in the last 20 years despite the move towards "cashless" purchasing technology.
The use of $100 bills increased by nine per cent over the past year, compared to a six per cent rise for $50 bills and two per cent for $20 bills.
The RBA has already launched a program to upgrade the security features of Australia's currency, which are now more than 20 years old and vulnerable to advances in digital scanning and printing technology.
The $5 note was replaced last year, while a new $10 note will be introduced in late 2017.
But the lengthy production schedule for the new currency means it will take at least until late 2019 for an updated $100 note to enter circulation.
The Australian Federal Police and RBA did not comment on the new counterfeit notes turning up in Melbourne.