WASHINGTON (Reuters) ? US regulators have cracked down hard on financial markets in the post-Enron period, but they were caught off guard ? again ? by the latest Wall Street scandal, this one at Refco Inc.

Refco does business in the US, Canada, Bermuda and Europe and the company lists its Bermuda office as a private mail box at 48 Par-la-Ville Road, the offices of Mailboxes Unlimited.

Last week's debacle at the giant futures and commodities broker is adding new urgency to questions about how US brokerages and exchanges are policed.

The problem, said regulation experts and market academics, is simultaneously one of too much oversight and not enough.

"While we might have a lot of regulation, we don't have necessarily appropriate regulation that has real power to change," said Richard Ferlauto, director of pension and benefit policy at the American Federation of State, County and Municipal Employees labour union.

Under the present system, "self-regulatory organisations" (SROs) ? such as the New York Stock Exchange and NASD ? deal with the daily routine of policing brokerages and exchanges, while government agencies handle the big issues.

Refco, for instance, was subject to regulation from a dozen separate US exchanges, the NASD and the NYSE's regulatory unit, as well as the Commodity Futures Trading Commission and the Securities and Exchange Commission.

Yet, none of these regulators detected or was in a position to prevent the sudden downfall of New York-based Refco, a company whose business interests sprawl across so many markets that no single overseer had a good handle on them.

"We have too many people watching the pot," said Junius Peake, professor of finance at the University of Northern Colorado's Monfort College of Business.

Refco's stock price fell 70 percent last week after it put Chief Executive Phillip Bennett on leave for allegedly shuffling $430 million in debt on and off the books through a firm he controlled with the help of a hedge fund. Bennett was arrested last week and charged with securities fraud.

The scandal at Refco comes as Wall Street is gearing up for a renewed push this fall against "redundant regulation."

Hoping for a sympathetic ear from new SEC Chairman Christopher Cox, the Securities Industry Association, which represents brokerages, is expected within weeks to release a major survey critical of overlapping market oversight.

The association's survey looks set to appear just as the SEC, supreme US markets overseer, refocuses its attention after a quiet summer on the same subject.

SEC Commissioner Annette Nazareth this month said securities firms are showing interest in a rough outline issued earlier this year by the SEC for reshaping the SRO system.

The SEC's outline presents several possibilities ranging from maintaining the status quo to throwing all oversight duties on the SEC itself, with intermediate scenarios in between.

It is difficult to imagine, most experts say, designing a highly centralised system of policing the markets that would not be captive to special interests and overly bureaucratic.

"You can't just ask, wouldn't it be better if a perfect government agency took over regulation?... Imagine if one did. What would be the outcome? I'm dubious," said Matthew Spiegel, professor of finance at the Yale School of Management.

One SEC idea that is attracting interest is expanding the power of the NASD, making it a sort of super-SRO, while also forcing SROs to have more independent voices on their boards.

"We can have self-regulation, but the only way to do it right is to create an uber self-regulator like the NASD writ large," said Donald Langevoort, professor of law at Georgetown University, who added such a move would be difficult as other SROs would be reluctant to give up their jurisdiction.