Howard Davies, ex-chairman of the Financial Services Authority, compared a proposed new agency to the World Trade Organization.
"Why in the finance sector do we not have something similar to the WTO?" Davies asked.
The current international agreement for setting and enforcing bank regulations, Basel II, has "absolutely no accountability," he told The Times of London.
In a separate speech in New York, British financial adviser Shriti Vadera, said the G20 process was, "like herding cats."
Vadera said some European banks have yet to admit to all the losses suffered in the financial crisis. "It's not the U.K. banks that have to come clean, but some of the Continental banks still have issues," she said.