The Enough Project - an arm of the Center for American Progress that combats crimes against humanity - placed Nintendo at the bottom of its conflict minerals ranking and also singled out HTC, Sharp, Nikon and Canon for a lack of progress.

"Nintendo has made no known effort to trace or audit its supply chain," the "Taking conflict out of consumer gadgets" report said. "Sharp, HTC, Nikon and Canon are taking initial steps to join industry efforts, but their progress remains far behind industry leaders."

Nikon declined to comment on the report. Sharp, HTC, Canon and Nintendo were not immediately available for comment.

The Enough Project scored companies on efforts to trace the source of the minerals and metals used, whether detailed audits of supply chains were being carried out, and if steps are being taken to develop an international conflict-free certification.

Other criteria included environmental rankings and whether support had been expressed for legislation on conflict minerals.

Intel, Motorola Solutions, HP and Apple "have moved forward to develop solutions despite delays in the legislative rule-making process by the U.S. Securities and Exchange Commission or SEC - an excuse that many other companies have used to explain their lack of significant action," the report said.

The 2010 Dodd-Frank financial reform law requires companies to disclose whether they use tantalum, tin, gold or tungsten from the Democratic Republic of the Congo. The U.S. Securities and Exchange Commission (SEC) is due to vote on August 22 on long-delayed guidelines needed to enforce the conflict minerals law.

Intel, Motorola Solutions, HP and Apple have taken steps including developing a smelter auditing program and an aid project for lagging smelters and aid projects to help develop a clean minerals trade, the report said.

The Enough Project said SanDisk, Philips, Sony, Panasonic, RIM and AMD have significantly improved their efforts "by surveying their suppliers, piloting due diligence, and joining the smelter audit program."

The U.S. conflict minerals rule has been arguably one of the most controversial rules in the Dodd-Frank law.

Companies would need to identify if any conflict minerals are used in their products. If the minerals are present, the companies would then need to conduct a due diligence check to track them through the supply chain to their origins.

War-torn DRC sits on large reserves of minerals used in electronics production and the Enough Project has warned that months of unrest in Congo's volatile east is hampering progress made in curbing the conflict minerals trade.

Tutsi-led M23 rebels are fighting government forces in the resource-rich eastern Congo and U.N. experts and Kinshasa have accused neighboring Rwanda and Uganda of supporting the uprising. Both countries have rejected the allegations.

The Enough Project has said the armed groups in eastern Congo were still generating income by smuggling tantalum, tin and tungsten through Rwanda.

(Reporting by Michelle Nichols; Editing by Phil Berlowitz)

• A Permanent Economic Emergency