Greenspan expects more collapses

"There's no question that this is in the process of outstripping anything I've seen, and it is still not resolved," Greenspan said.

He described the crisis which is embroiling Wall Street and the City as "probably a once in a century event".

Greenspan told ABC television the US government would try to avoid pumping in more taxpayers' money into Wall Street bailouts.

"We shouldn't try to protect every single institution," he said. "The ordinary cost of financial change has winners and losers."