Insider trading "appears to be rampant" among Wall Street securities professionals, she added.
Alice Fisher, assistant attorney general with the Justice Department's criminal division, echoed Thomsen's sentiment and said: "The number of insider trading cases don't seem to be going away."
In the past year, SEC enforcement lawyers have brought increasing numbers of insider trading lawsuits and settlements. Recent high-profile cases include charges against a husband and wife in Hong Kong for trades in Dow Jones & Co Inc shares ahead of News Corp's $5 billion takeover bid, and guilty pleas from three former Countrywide Financial Corp executives for trading company shares ahead of a disappointing profit report.
Also, in March U.S. prosecutors charged 13 people, including employees at top Wall Street banks UBS, Morgan Stanley and Bear Stearns Cos Inc in what they called one of the most pervasive trading rings since the 1980s. The SEC also brought civil charges against 11 people, as well as against three hedge funds.
Insider trading involving hedge funds is the focus of one of the four internal working groups the SEC has set up to tap expertise and coordinate efforts throughout the agency. The $1.8 trillion hedge fund industry guards its secrecy and complex trading strategies.