Counterfeiting of banknotes in Australia spiked by 63 per cent over the year to June 2015, the Reserve Bank of Australia said in its annual report.One enterprising gang - blandly described as "a single production source of counterfeits" by the RBA - was behind the surge."Some arrests have been made in relation to this production source, andthe police are continuing to investigate the matter," it said. The RBA said that in 2014/15, "around 37,000 counterfeits, with a nominal value of nearly A$2 million, were detected in circulation."Counterfeiters will soon have to update their artwork and other methods, with the first two denominations (the $5 and $10 notes) of the new Australian banknote series expected to be issued in 2016/17.