The European Union has been urged to crack down on illegal imports of conflict minerals from the Democratic Republic of Congo (DRC) after uncovering evidence of breaches of existing regulations.

Advocacy group Global Witness (GW) said the "risk remains high" that EU mineral imports are used to fund militias and state repression in multiple countries.

The EU has passed legislation to prevent armed groups from benefiting from trade in tin, tungsten, tantalum and gold, metals used in electronics and making clean energy technology.

The EU's Conflict Minerals Regulation will come into full effect in 2021, requiring due diligence on companies importing minerals from conflict-affected countries. Member states are responsible for carrying out inspections and imposing sanctions if rules are breached.

But in a recent review, the European Commission admitted that an external study found "limited impact on local stakeholders". It also found "delays" and "implementation challenges".

Separately, researchers from the Antwerp-based International Peace Information Service found that the impact of the regulation was "almost negligible and that the illegal mineral trade continues to fund conflict."

GW traced the supply chain of a European trader sourcing minerals from eastern Democratic Republic of Congo, where militias involved in killing and raping civilians use the mineral trade to fund their activities.

Documents obtained by the rights group and seen by the Guardian appear to show that a supplier sourced wolframite, a type of tungsten ore, from Nzibira in South Kivu province in early 2023 and passed it on to European buyers. Home Traxys Europe, but was denied the charge.

Traxys said it is "firmly committed to working only with responsible and conflict-free supply chains" and has "invested significant effort and resources" in doing so.

Congolese government officials told GW that during 2023, minerals from unverified mines were incorrectly labeled as being of reliable origin.

GW claims EU regulations are not being properly enforced as the bloc seeks to shore up supplies of critical minerals as it transitions to more sustainable energy.

Emily Stewart, director of policy at GW, said: “The EU created this regulation to stop the import of conflict minerals. But not enough is being done to ensure it works.

"The regulations allow companies not to bother with due diligence because there appear to be no proper checks on what they are doing, nor on the consequences of their activities."

The group urged the EU to strengthen enforcement, improve import transparency and impose sanctions on companies that do not comply.

Safanto Bulongo of Max Impact, a Congolese organization that monitors natural resource governance, said nothing has changed in the Democratic Republic of Congo since the regulation came into effect.

"EU regulation is stillborn; the Democratic Republic of Congo knows nothing about it," he said. "There are no efforts to improve the situation. Companies from the northern hemisphere are not taking due diligence seriously - the impact is war."

Brongo added that if the EU was serious about enforcing strict regulations, finished products should be inspected, as minerals from the Democratic Republic of the Congo enter Asia before entering Europe as part of electronic components.

Last month, the Congolese government filed criminal charges against Apple in France and Belgium, accusing the company of using conflict minerals that were laundered through international supply chains. Apple has denied the accusations and said it has told suppliers to stop sourcing the minerals from the Democratic Republic of Congo and Rwanda.

European Commission spokesman Olof Gill said that member states are closely monitoring the implementation of the regulation and "Member states regularly inform companies of the corrective measures required to meet their legal obligations."

"The EU review concluded that a more harmonized sanctions regime is not necessary at this stage," he said. "NGOs are encouraged to report any breaches of the regulations to the responsible (member state) so that appropriate action can be taken."