The Energy Financing Team (EFT) is headquartered in London but works largely in the Balkans, where the deregulation of energy markets has given it plenty of opportunity to do business.
Serbian businessman founded the firm in 2000, and it has now grown into 17 countries, nine of them in southeast Europe.
The company buys and resells energy and invests in generation units, transmission networks and mining. Recent major projects were all in Bosnia, including a hydroelectric supply tunnel, investment in a coal mine, and plans for the construction of a thermo-electric power plant near that mine.
The company also has controversial plans to build a dam on Montenegro's Tara River canyon, the second-deepest canyon in the world.
EFT has faced allegations of corruption from authorities from the U.K, the U.S. and the Balkans.
In 2003, the Office of the High Representative in BiH published a special audit of Elektropriveda Srpske, the Republika Srpska's state-owned power utility. The audit questioned EFT's relationship with the utility, saying EP RS had sold power to EFT below market price.
That audit report led the Serious Fraud Office in the UK to investigate EFT on allegations that it broke a British anti-bribery law.
The prosecutor's office in the Court of BiH also investigated the firm for corruption, but dropped the three-year-old case in 2006.
EFT has denied all wrongdoing in these cases, and it has not been charged with any crime.