Flickr/Center for American Progress
Blair brokered multi-million pound deals for PetroSaudi with senior Chinese officials through his company Tony Blair Associates, according to The Sunday Times.
His lucrative dealings, discovered in a leaked 21-page document, are said to have been agreed in November 2010 in Beijing and also came with a 2% commission on transactions.
PetroSaudi is registered in the Cayman Islands, a well-known tax haven, and apparently avoids 85% of oil and gas company taxes.
Blair's role as a peace envoy in the Middle East, after sending British troops to Iraq in 2003, is now under further scrutiny.
This is believed to be the first time a contract negotiated by Blair has been revealed; there are notes the work lasted just a few months.
The Sunday Times explains a source informed the paper that Blair "has got deep ties to the Middle East" and spoke of a "confidential engagement to help develop business in China."
A spokesperson for Blair responded: "Tony Blair Associates worked for PetroSaudi for a period of months over four years ago."