The letter addressed to Prime Minister David Cameron said a lasting legacy of the London Games would be re-focusing the energy that went into carrying off the event on to the effort to feed the world.
"The eyes of the world are on London 2012," said the letter. "The best legacy the Games can leave is a world where strong, healthy and well-nourished children can achieve their full potential in life."
The letter was signed by various British Olympic medalists and other athletes, including runner Tirunesh Dibaba of Ethiopia.
The BBC said Cameron has said in the past that Britain should take a lead role in hunger eradication, and the United Kingdom will be in a position to do that next year when it assumes the presidency of the G8.
Cameron hosted a "hunger summit" in London on Sunday -- the final day of the Olympics -- that included representatives of several nations.