The Lloyds TSB offshore accounts in the name of the Angolan state oil company, Sonangol, include cash payments by the companies to the government in return for exploration permits in the booming Angolan deep-water oil fields.

The Guardian said the Angolan authorities have been "strenuously" trying keep the payments secret as pressure mounts on oil companies to disclose these huge "signature bonus" payments.

"It is estimated that, apart from normal revenues, almost $US1.2 billion has been scooped up in the last three years by the regime of President Dos Santos by auctioning exploration blocks off the West African coast," the paper said.