John Walsh, chairman of the Massachusetts Democratic Party, said Brown "watered down Wall Street reform just enough so that the same high rollers who gambled away our economy are right back at it," the Boston Herald reported Tuesday.
Walsh also criticized Brown, battling Democrat Elizabeth Warren to keep his Senate seat, for failing to list members of a "secretive" New York City finance team.
Brown's campaign said Monday the New York City fundraising committee was one person, entrepreneur Anthony Scaramucci, who held a March 12 fundraiser event for the Massachusetts Republican.
Scaramucci briefly worked at Goldman Sachs and Lehman Brothers, two troubled firms at the fore of the 2008 financial collapse. Scaramucci, now with investment firm SkyBridge Capital, donated $4,600 to President Barack Obama in 2008 and gave Brown $4,800 in 2010.
Warren, a well-known consumer advocate, called for JPMorgan Chief Executive Officer Jamie Dimon to resign from the board of the New York Federal Reserve Bank after the firm's executives announced they lost $2 billion because of risky investments.
Jim Barnett, Brown's campaign manager, said Brown believes Dimon will be held accountable by the bank's public shareholders.