Human rights activists on Wednesday said European efforts to stop the trade in so-called "blood metals" were a "step backwards" that would not prevent profits from minerals being used to fund conflicts.
Amnesty International criticised the European Commission's new self-certification scheme for importers of tin, tantalum, tungsten and gold for only being voluntary and failing to include a broad enough definition of human rights abuses.
Brussels-based Central African NGO EurAc said the voluntary nature of the scheme suggested the Commission was "more interested in economic interests" than the people of war-torn countries.
"Blood metals" or "conflict minerals" refer to the way in which the mining of resources can worsen violent conflict in unstable areas where armed groups control mines, use forced labour or extort money from the trade.
One in five of the world's conflicts combine violence with natural resources, according to a study by the Heidelberg Institute for International Research in Germany.
One of the best-known cases is Democratic Republic of Congo, where mineral sales have helped fund decades of militant violence.
Under the new scheme, European mineral importers who sign up will have to check where their minerals are sourced.
However, a 2013 study revealed that in the EU due diligence was not a common practice for mineral importers, with only 12 percent of companies listed on EU stock exchanges referring to conflict minerals on their websites.
Seema Joshi, Amnesty's business and human rights director, said the plan was "substantially weaker" than existing standards set by the OECD and already endorsed by EU governments.
European officials hit back at the criticism on Monday, saying that "we are not naive and we should give this scheme a chance," adding that it will be reviewed after three years to assess whether criteria need to be "tightened".
"We are committed to preventing international trade in minerals from intensifying or perpetuating conflict," EU foreign affairs chief Catherine Ashton and EU Trade Commissioner Karel De Gucht said in a joint statement.
The new rules specifically target the EU's electronics and lighting sectors, who are the biggest users of the metals listed by the Commission.
De Gucht also rejected the suggestion that the measures were weaker than the US's Dodd-Frank Act from 2010, which required publicly listed companies to declare the origin of any potential "conflict minerals" they use.
"The EU carrot rather than the stick approach is intended to complement Dodd-Frank by... providing pressure points in different parts of the supply chain to ensure the scheme is used," he said.
Industry representative body Euromines supported the move, saying its members are already committed to high levels of transparency when purchasing minerals from conflict areas.
"Our members are already undertaking efforts to ensure responsible sourcing of minerals and recognise the need for responsible production and sourcing of natural resources," the organisation said in a statement.