The Reserve Bank of Australia's index of commodity prices fell by 1% in foreign currency terms between November and December.
Lower prices for gold, iron ore and coking coal were the main reasons for the latest fall.
The fall in December brought the decline through 2013 to 4% .
AAP reports steeper falls over the preceding 1½ years, mean the index was 25% lower than an all-time high set in July 2011.
The last time the index recorded a lower reading than December was in April 2010.
The foreign currency price index price index is measured in terms of special drawing rights (SDRs), an average of four major currencies - the US dollar, euro, Japanese yen and British pound.
The fall in commodity prices in foreign currency terms has been only partly offset by a lower exchange rate.