Football Leaks also claimed the 41-year-old reacted angrily when friend and PR advisor Simon Oliveira suggested he put 1 million dollars (£800,000) into a prize-giving Unicef dinner in Shanghai.
Beckham allegedly replied: "I don't want to put my personal money into this cause."
Football Leaks claimed he added: "To pour this million into the fund, is like putting my own money in. If there was no fund, the money would be for me. This f****** money is mine."
French investigative site Mediapart, which published the Football Leaks material, alleged that Beckham wanted to use his personal fund - named 7 after his former squad number - to promote his business activities.
"Humanitarian causes were just a stepping-stone for his personal affairs, and to project his image among advertisers," claimed a source close to the leaks.
Football Leaks handles some 18 million confidential documents handled by a consortium of international media, including Mediapart in France.
Like Wikileaks it chooses to "dump" selected documents when it considers the time is appropriate.