Two Democrats expanded their inquiry into Wal-Mart’s alleged bribery of Mexican officials Wednesday, questioning two trade associations about their lobbying efforts to amend the Foreign Corrupt Practices Act.

Reps. Henry A. Waxman (D-Calif.) and Elijah E. Cummings (D-Md.) wrote separate letters to the U.S. Chamber of Commerce and the Retail Industry Leaders Association regarding their work to revise the Watergate-era statute, which bans bribery of foreign government officials.

The letter follows a report in The Washington Post showing that a top Wal-Mart official sat on the board of the Chamber’s Institute for Legal Reform as that organization sought to change the FCPA.

A senior Wal-Mart executive also serves as a director at the Retail Industry Leaders Association.

In their letters, the lawmakers expressed concern that there might be a conflict of interest if Wal-Mart was backing a campaign to soften enforcement of the statute at the same time corporate executives were examining their own corruption allegations in Mexico.

Wal-Mart’s activities in Mexico were brought to light by a New York Times report last weekend showing that senior executives at the company squashed an internal investigation into allegations of bribery in 2005. After that report, the two congressmen asked for more information from the company and an opportunity to meet with Wal-Mart executives.

A Wal-Mart spokesman said Wednesday that the firm will respond to the lawmakers’ request soon. He stated that the firm has not participated in the effort to lobby to change the FCPA.

“Wal-Mart has never lobbied on FCPA,” said David Tovar, vice president for corporate communications at the retail firm. “Simply because Wal-Mart is a member of an organization does not mean we agree with every position they take.”

He said that Wal-Mart’s corporate secretary, Thomas Hyde, who served as a director of the Chamber’s Institute for Legal Reform, did not cast a vote on the FCPA campaign.

Hyde, who also served as Wal-Mart’s top ethics officer, was named in the New York Times story as one of the Wal-Mart officials aware of the 2005 bribery reports.

A Chamber spokesman said Wednesday that the group’s activities were on behalf of the entire business community and represented a desire to improve compliance with the FCPA.

“While the law serves an important purpose, its ambiguities and current enforcement practices make it more difficult for American businesses to compete in an increasingly global marketplace,” said Bryan Quigley, a spokesman for the Chamber’s Institute for Legal Reform, which is leading the lobbying effort.

RILA spokesman Brian Dodge said the organization will respond shortly to the congressional request.

“RILA regularly communicates with policymakers on dozens of issues affecting our members, their employees, and their customers,” he said in a prepared statement. “RILA believes that adherence to the law is essential and that further clarity and predictability regarding FCPA enforcement” will help compliance.

Still, several experts on the law say the changes being lobbied for would eviscerate the statute by limiting prosecutors’ enforcement options.