Crisis fears linger five years on from Lehman

"It's unlikely to happen on the same scale today. But could it happen in five, ten or fifteen years' time? Absolutely, if we do not regulate these too dangerous to fail banks right, and if we don't actually start enforcing the law against them," he added.

On September 15, 2008, the collapse of Lehman Brothers - the largest bankruptcy filing in U.S. history - led global financial markets into the worst crisis since 1929.

While U.S. and European regulators have taken steps to crack down on excessive risk taking in larger banks, and to enforce higher capital requirements, concerns remain that not enough has been done. Democratic Senator Elizabeth Warren, for instance, accused Congress this week of being too lax on forcing U.S. banks to comply with new regulations.

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