Volkswagen's worldwide pollution cheating has been exposed in large part thanks to independent campaigners, a growing force in the scrutiny of multinationals whose activities can escape the gaze of official regulators.
The revelations shaking Volkswagen, the world's biggest automobile manufacturer by sales with a workforce of 590,000 people, can be traced to the work of the US-based group International Council on Clean Transportation, which has a worldwide staff of 27.
Working with engineers at West Virginia University, they uncovered significantly higher levels of pollution spewing out of the exhaust pipes of cars on the road than those recorded in official tests.
Drew Kodjak, executive director of the non-profit group, said the discrepancies were found for cars in Europe.
"It's up to the regulators in Europe to figure out whether or not there's a defeat device," he said in an interview with AFP this week.
"In the United States, our research triggered further investigation, but the defeat software was uncovered by the regulators."
Non-governmental organisations have become key to exposing such scandals, said Yann Louvel, coordinator of BankTrack, a network of organisations and people worldwide tracking banks' activities.
- List of targets grows -
The list of multinationals feeling the heat from campaign groups is growing.
French construction group Vinci has been attacked by Paris-based Sherpa, self-described defender of the victims of economic crimes, over working conditions at its construction sites for the 2022 World Cup in Qatar. Vinci has denied the allegations and sued for defamation.
Non-governmental organisations pursued Western brands over the conditions in clothes factories overseas after the 2013 Rana Plaza garment factory collapse in Bangladesh, which killed more than 1,100 people. The campaigns helped to push companies to contribute to a $30 million a victims' compensation fund.
Food giants have been forced to review their palm oil operations following campaigns by environmental groups warning of the dangers of deforestation.
After coming under heavy criticism, Apple in 2012 asked labour watchdog Fair Labor Association to assess the conditions for workers at factories of its major Chinese supplier Foxconn.
Non-governmental organisations, or NGOs, have also alerted national authorities to the ways multinationals such as Starbucks or Google are able to enjoy low tax rates.
- 'How could they miss it?' -
"NGOs have become more professional and stronger," said Oxfam charity campaigner Nicolas Vercken.
"Ten years ago when we asked for a meeting with the French foreign ministry they expected us to come asking for money for a humanitarian catastrophe," Vercken said.
"Today they see us for our expertise or because we are seen as a possible nuisance," he said.
The rising professionalism of campaign groups was illustrated by the Volkswagen scandal: the International Council on Clean Transportation is staffed by former automobile industry managers, bristling with diplomas and sporting ties.
Sherpa, for example, relies on its network of lawyers and legal experts to bring corporations to court with sophisticated legal arguments, said its director, Laetitia Liebert.
Like other NGOs, Sherpa uses social networks to lend "strength, leverage and protection" when it targets big companies, she said.
For BankTrack's Louvel, the Volkswagen scandal shows the important role played by NGOs.
"But you also wonder how the traditional regulators could have missed it," he said.
"It's worrying given the small resources that NGOs have," Louvel said. "It is a bit easy to rely on us."