Jan. 9 (Bloomberg) -- Patrick Degorce, co-founder of The Children’s Investment Fund Management, resigned after the activist hedge fund suffered its biggest annual loss.

Degorce, who turned 40 this week, left the $15 billion fund on Jan. 1, according to a U.K. regulatory filing that didn’t give a reason for his departure. Degorce and co-founder Christopher Cooper-Hohn didn’t return calls seeking comment.

In five years at London-based TCI, the French native was involved in some of its highest-profile campaigns. They included pushing for the breakup of Amsterdam-based bank ABN Amro Holding NV, which led to its sale, and the removal of senior executives at Deutsche Boerse AG, operator of Germany’s main stock exchange. TCI, Frankfurt-based Deutsche Boerse’s largest investor, was hurt as the stock fell 62 percent last year.

The fund, which gives a portion of its profits to children’s charities, fell 43 percent in 2008, including a $130 million loss in October to sell its investment in Electric Power Development Co, Japan’s biggest electricity wholesaler. The fund had average gains of 42 percent a year from 2003 to 2007.

TCI has told investors that Degorce retired because of “health problems,” the Wall Street Journal reported on its Web site, citing a person familiar with the fund. His departure was reported earlier by Financial News.

Before starting TCI, Degorce spent seven years at Merrill Lynch & Co. asset-management unit, where he ran the $3 billion European Dynamic Fund.

Degorce is an active director in Ingenious Film Partners LLP, according to U.K. filings. The company is a vehicle for investing in U.K. movie productions.

To contact the reporters on this story: Tom Cahill in London at tcahill@bloomberg.net.

Last Updated: January 9, 2009 15:04 EST