WASHINGTON  President Obama signed a sweeping expansion of federal financial regulation on Wednesday, signaling perhaps the Democrats’ last major legislative victory before the midterm elections in November, which could recast the Congressional landscape.

Within minutes of the bill signing, several Wall Street groups were leveling criticism at the new regulations, reflecting Mr. Obama’s increasingly fractious relations with corporate America.

The Business Roundtable complained in a statement that the law “takes our country in the wrong direction” and may discourage investment and job growth, echoing concerns made by the United States Chamber of Commerce and other business organizations.

In a signal that Wall Street is ready to keep lobbying as regulators work out the details of how to apply the new law, Larry Burton, the roundtable’s executive director, said: “We will work with President Obama and policy makers to ensure this legislation is implemented in a manner that continues to promote sustainable economic growth and job creation.”