"I want to say that capitalist economics is false economics. Now they are trying to reform the system, the very system that caused the crisis," Ahmadinejad told reporters during a visit to Kazakhstan.
"We are interested in a new financial system based on justice. A real economic system."
In a fiery speech, the Iranian leader, speaking through a translator in Kazakhstan's capital Astana where he is on a state visit, blasted the world's main economic powers for burdening the world with their economic mistakes.
In a surprise move, Ahmadinejad became the first major world leader to back a plan put forward by Kazakh President Nursultan Nazarbayev last month to create a single world currency.
"It's a wonderful proposal. We consider it a good and correct idea. The world needs a single currency, a real currency."
Nazarbayev first called publicly for the creation of a new global currency, the "acmetal," in an article published in Russia's official daily Rossiskaya Gazeta in February.
At a conference in March, Nazarbayev argued the world required "an absolutely new global currency system."
His idea immediately won support from Robert Mundell, the Nobel prize-winning Canadian economist and a key intellectual architect of the euro currency, who said he was "right on track" with the scheme.
Ahmadinejad blamed Western immorality and shady financial instruments — he described their use as "selling paper" — for the global economic crisis.
"I want to say that this is a moral crisis and not a crisis of finances," the Iranian leader said.