He also noted that previous financial regulations were "half a century or more old," and that the financial crisis emerged from an industry that was poorly regulated and not well understood.
Lew's comments came during an interview that also touched on immigration reform, revelations that the Internal Revenue Service had singled out conservative groups for extra scrutiny and the broader economic recovery.
Some legislators worry that more needs to be done.
Sens. Sherrod BrownSherrod BrownDems press Trump to support ‘Buy America’ provision in water bill Sanders vs. Trump: The battle of the bully pulpit Fight over 'Buy America' provision erupts in Congress MORE (D-Ohio) and David VitterDavid VitterPoll: Republican holds 14-point lead in Louisiana Senate runoff Louisiana dishes last serving of political gumbo Trump tweets about flag burning, setting off a battle MORE (R-La.) introduced legislation in April to tighten controls on big banks. The bill would increase the amount of money most banks need to hold in reserve, limit financial institutions' ability to transfer money between affiliates and reduce burdens for small institutions.