In the letters Reps. Spencer Bachus and Judy Biggert sent to the Treasury and the Federal Reserve, the GOP lawmakers challenge the legality of Elizabeth Warren's authority to set up the new Consumer Financial Protection Bureau.

Bachus and Biggert have urged the inspectors general at the Treasury and the Fed to investigate how Elizabeth Warren, whom President Obama made special White House adviser in September, has been setting up the Consumer Financial Protection Bureau, a new agency created under the summer's financial reform legislation.

As she leads the search for the agency's first director, Warren effectively serves as its interim head.

By appointing Warren as special adviser in September, the president "undermined" the Constitution, Bachus and Biggert contend, in two nearly identical letters dated Nov. 22. From the letters:

"First, the President's decision to appoint Professor Elizabeth Warren as a special advisor to the Secretary of the Treasury and as a senior advisor in the White House with lead responsibility for establishing the Bureau, hiring its staff, and setting its agenda -- as opposed to nominating the director of the Bureau, as contemplated by the Act -- circumvented the advice-and-consent process and undermined one of the key checks and balances in our Constitution. While the Act confers upon the Secretary of the Treasury limited interim authority 'to perform the functions of the Bureau' (Section 1066(a)), Professor Warren is now exercising that authority."

The GOP lawmakers say Warren is overstepping her authority. But Warren has responded to this criticism in the past.

As she explained on PBS in early October, her current job was specifically created by law. "There are two jobs on the table. And they were always there by statute. One certainly is the director of the agency," Warren said. "There is a second job that was available. And it's clear in the statute. Somebody is supposed to get out there and get that agency going. And the truth is, one has a cool title, but the other one gets to work right now."

A spokesperson for the House Financial Services committee, who speaks for Bachus on financial services issues, didn't immediately respond to requests for comment.

Zachary Cikanek, press secretary for Biggert, said the agency's eventual leader should face a full confirmation process. "What we would like to see is for the person with lead responsibility of the Bureau to be somebody nominated by the president and confirmed by the Senate," Cikanek said.

Bachus is a leading contender to replace Rep. Barney Frank (D-Mass.) as chairman of the House Financial Services Committee. During the 2009-2010 election cycle, his campaign received $132,200 from the securities and investment industry, and $80,800 from commercial banks, according to Open Secrets. His top contributors included Capital One, Credit Suisse, Wells Fargo and Bank of America, which each donated $10,000 to his campaign, Open Secrets says.

READ the letter to Treasury below: