Stung by claims that it missed discovering a massive fraud, the Securities and Exchange Commission is now poring over Bernard Madoff’s books, trying to unpick an alleged Ponzi-like operation that appears to have lost investors tens of billions of dollars.

But it was the SEC’s decision in the 1990s not to take a stand on the controversial issue of “payment for order flow” that helped fuel the rise of Bernard Madoff Investment Securities, the successful broker-dealer operation two floors above Mr Madoff’s private fund operation in Manhattan.