Australia's dollar slumped below 74 US cents for the first time in six years overnight, as the US dollar continued to go from strength to strength.

The Aussie briefly dipped to US73.98¢ just after midnight AEST on Wednesday morning before recovering. At 6am AEST, it is fetching around US74.50¢. Overnight, the US greenback hit a five-week high against most major currencies on the back of continuing global concerns, as unfinished efforts to address Greece's debt crisis and a rout in commodities pushed investors into the safest assets.

"Further depreciation seems both likely and necessary, particularly given the significant declines in key commodity prices.": RBA Governor Glenn Stevens. Credit:Louise Kennerley

The Australian dollar's fall comes after RBA Governor Glenn Stevens kept interest rates at a record low for a second month on Tuesday and said a weaker currency is still needed.

The currency has fallen against all except one its 16 major counterparts this month after the Reserve Bank of Australia left its benchmark at 2 per cent Tuesday as economists forecasted.