Speculation is mounting that Warren, a White House adviser who is helping to put the CFPB together, may not be nominated because she might not win Senate confirmation. House Financial Services Committee ranking member Barney Frank (D-Mass.), whose Wall Street reform bill created the CFPB last year, said this week that her confirmation is in doubt in the Senate, and speculated that President Obama may not nominate her for that reason.

Warren testified last week before the Financial Services Committee, where she indicated opposition to Republican plans to create a five-member commission to head the CFPB. She reiterated arguments against that idea on Tuesday by noting that the new agency's decisions will be able to be overturned by other agencies. "We have nothing like that anywhere in government," she said.

She also broadly rejected Republican claims that the CFPB is worrisome because it would be the most powerful agency ever created.

"The notion that somehow if you're speaking out on behalf of consumers we need to beat you down a little more, there need to be fewer powers … that just seems wrong to me," she said.