European legislators on Wednesday unexpectedly voted in favour of a law requiring firms to ensure they do not use so-called conflict minerals from Africa and other areas that end up funding warlords.
The legislation for compulsory regulation of the use of tungsten, tin, tantalum and gold, which are often used in computers and mobile phones, will however face a tough test to get past EU governments.
"I must confess that it's been one of the most intense moments I've experienced since becoming a member of the European parliament," said Socialist Gianni Pittella of Italy, who leads the second biggest bloc in the assembly.
"The fact that this got through is a source of great satisfaction," Pittella said.
Applause broke out as lawmakers at the last minute passed amendments calling for compulsory ethical sourcing of materials from conflict areas like the Democratic Republic of Congo, Colombia and Afghanistan. The amendments passed by a vote of 378 to 300, with 11 abstentions.
The campaign has been backed by dozens of humanitarian groups and star campaigner Denis Mukwege, a surgeon in DR Congo who last year won Europe's top rights prize for his work treating victims of mass rape.
Also supporting it is Edward Zwick, the Hollywood producer of the hit Leonardo DiCaprio film "Blood Diamond" about how gemstones financed the 1990s war in Sierra Leone.
- Unexpected victory -
The European Parliament in Strasbourg, France, had been expected to pass a watered down motion that would have made it largely voluntary for firms in Europe to responsibly source the metals.
The biggest group in parliament, the centre-right European People's Party of European Commission chief Jean-Claude Juncker, and business lobbyists had opposed binding rules.
But leftist and green Euro-MPs said they had lobbied wavering right-wing counterparts to swing the vote.
Campaign group Global Witness said compulsory regulation would mean that Chinese and other non-EU firms that want to export goods to Europe would be under greater pressure to check the sources of minerals.
The EU bill is inspired by the Dodd-Frank Act, a 2010 US financial reform law under which US companies must inform regulators if they use metals from DR Congo or neighbouring countries.
The European Commission had supported a voluntary system for all companies, but the parliament's trade committee firmed the proposal up last month by requiring mandatory controls from the estimated 20 smelters and refineries in the bloc.
The leftist groups then pushed for it to be mandatory across the board.
- Tech giants -
Lobby group Business Europe said the voluntary approach encouraged companies to "develop responsible management schemes."
Tech giants like Apple and Hewlett Packard have previously made efforts to ensure the traceability of their supplies.
There have also been criticisms of the Dodd-Frank act for having unintended side effects, such as causing businesses to pull out of DR Congo altogether, leaving thousands of miners out of work and vulnerable to recruitment by armed groups.
"The Dodd-Frank act showed the folly of a mandatory approach," said Daniel Dalton, a member of the European Conservatives and Reform Group.
"A mandatory approach will fundamentally damage the economy of conflict-affected areas around the world," he said.
The tougher legislation passed by the European Parliament now has to be discussed with the member states and the European Commission, the executive of the 28-member EU, officials said.
Pittella and his colleagues now plan now to lobby the 28 member states in what they said would be an equally hard campaign to win them over.
Compulsory regulation would also mean that Chinese and other non-EU firms that want to export goods to Europe would be under pressure to check the sources of minerals, said campaign group Global Witness.