A spike in the number of travellers stocking up on the US dollar has caused a rush on the currency at smaller foreign exchange businesses.

A Melbourne branch of currency exchange company Travel Money temporarily ran out of US dollars this week.

“Demand has gone through the roof,” said Travel Money team leader Rory Tidball. “The last weeks have definitely been the busiest consecutive days we've ever experienced.”

The surge in demand has topped the level of activity seen when the dollar last approached parity with the greenback in 2008, Mr Tidball said.