Oil giant Shell had "access to everything" being done by the Nigerian government because it had staff in every relevant department, according to the latest US embassy cables revealed by WikiLeaks.
The wires published by the Guardian refer to comments made by Ann Pickard, Shell's then vice-president in Africa, that the government had "forgotten" that the global firm had seconded Shell employees to various ministries.
The notes suggest Shell staff were able to gather inside information about the dealings of the oil-rich state.
In the confidential cable from October 2009, the ambassador wrote that Ms Pickard said Shell had received a copy of a letter from a Nigerian government adviser to the Chinese rejecting an offer for oil exploration blocks.
The cable said: "Pickard said Shell had good sources to show that their data had been sent to both China and Russia.
"She said the GON (Government of Nigeria) had forgotten that Shell had seconded people to all the relevant ministries and that Shell consequently had access to everything that was being done in those ministries."
The ambassador, named by the Guardian as Robin Renee Sanders, also reported Shell was "producing 663,000 barrels per day as of October 13, including the Bonga field".
Among the cables were memos indicating Shell had shared intelligence with the US about "militant unrest" as well as asking for information about rival Russian energy company Gazprom.
In a cable from September 2008, the ambassador wrote: "Pickard asked for USG (US government) information on Gazprom's interest in Nigeria.
"She had heard from contacts in the British government that the GON has promised Gazprom access to 17 trillion cubic feet of natural gas.
"Pickard said that that amount of gas was only available if the GON were to take concessions currently assigned to other oil companies and give them to Gazprom. She assumed Shell would be the GON's prime target."
The cable added: "Pickard has repeatedly told us she does not like to talk to USG officials because the USG is 'leaky'."
A spokeswoman for Shell said the company would not comment on the contents of the leaked cables.
In a statement to the Guardian it said: "You are seeking our views on a leaked cable allegedly containing information about a private conversation involving a Shell representative, but have declined to share this cable or to permit us sufficient time to obtain information from the person you say took part in the conversation on the part of Shell. In view of this, we cannot comment on the alleged contents of the cable, including the correctness or incorrectness of any statements you say it contains."