The charitable foundation launched by Bill Gates, the world's richest man, has lost around $10bn, or nearly a quarter of its assets due to stock market losses and shrinking donations from Gates and his wife Melinda.

The Bill and Melinda Gates Foundation Trust said in its annual audited report filed yesterday that its assets totalled $29.8bn at the end of 2008, compared with $38.8bn at the end of 2007.