WASHINGTON — Republican and Democratic House members said Monday that the alleged $50 billion fraud involving Wall Street figure Bernard Madoff reflects deep, systemic problems at the Securities and Exchange Commission.

Inspector General H. David Kotz said he is so concerned about the SEC’s failure to uncover Madoff’s alleged Ponzi scheme that the IG is expanding the inquiry called for last month by SEC Chairman Christopher Cox. Cox had pushed the blame squarely onto the SEC’s career staff for the failure to detect what Madoff was doing.