By Jessica Wohl

ROGERS, Ark., May 31 (Reuters) - Wal-Mart Stores Inc , the world's No. 1 retailer and the biggest seller of firearms in the United States, is dropping out of a U.S. conservative advocacy group that has been a lightning rod over voting and gun laws.

Wal-Mart said late Wednesday it is suspending membership in the American Legislative Council (ALEC), which the retailer joined in 1993.

ALEC sparked controversy recently because of its involvement in voting laws and in "stand your ground" gun laws, including the one under scrutiny in the Florida killing of unarmed 17-year-old Trayvon Martin in February.

A coalition of liberal advocates targeted the group for its support of the self-defense laws.

ALEC, which serves as a forum for corporations and mostly Republican state lawmakers and lobbyists to discuss model legislation, has been criticized by liberals for promoting laws that require photo identification to vote.

ColorOfChange, a liberal advocacy group for black Americans, has said the voting laws put the poor and minorities at a disadvantage.

In April, ALEC said it was abandoning the committee that worked on "public safety and elections" to focus on the economy. Despite the change, Wal-Mart decided it was no longer focused on the same issues as the council.

"Previously, we expressed our concerns about ALEC's decision to weigh in on issues that stray from its core mission 'to advance the Jeffersonian principles of free markets,'" Maggie Sans, Wal-Mart vice president of public affairs and government relations, said in a May 30 letter addressed to ALEC's national chairman and executive director.

"We feel that the divide between these activities and our purpose as a business has become too wide. To that end, we are suspending our membership in ALEC."

Sans, who is also giving up her role as secretary of ALEC's private enterprise board, did not specify the issues that caused the split.

Wal-Mart has benefited from ALEC campaigns involving taxes, commerce and technology.

"While we are disappointed in Walmart's decision, we understand the unique pressures they are under," said spokeswoman Kaitlyn Buss.

"However, as we announced in April, ALEC is solely focused on limited government, free-market solutions in the states that create jobs and improve the economy."

ALEC believes its member companies are being targeted with campaigns that produce "manufactured outrage and the facade of grassroots support," she added.

Wal-Mart is the latest group to back away from supporting ALEC, including Coca-Cola Co, Kraft Foods Inc, McDonald's Corp, Procter & Gamble Co and the Bill and Melinda Gates Foundation.

Wal-Mart's announcement comes as it grapples with recent allegations of bribery at its Mexican unit and a management decision to squelch an investigation -- a likely subject at the annual shareholders meeting on Friday.