Despite a well-publicised drive to clean up corruption by multinational companies in Africa, Britain's export credit agency did little to investigate serious allegations of bribery at a huge Nigerian gas project it helped underwrite, according to internal documents released to the Financial Times.

The Export Credits Guarantee Department did little more than ask Halliburton - one of four companies accused of paying $172m (€142m, £94m) in bribes - whether the allegations were true, according to the papers obtained under the Freedom of Information act.