A London-based lobbying firm has become the focus for an international criminal investigation into allegations of corruption by western engineering companies over a huge dam project in Africa. The allegations include whether promises of bribes were made to Ugandan MPs by agents acting for a Scandinavian consortium over the building of the $580m (£342m) Bujagali dam on the river Nile. It is the largest private finance project in east Africa and one of the World Bank's most prestigious developments on the continent.