The LA Galaxy star will deliver a letter signed by some of the most famous and influential celebrities in the world, including Claudia Schiffer, Whoopi Goldberg and Robbie Williams.
Beckham, a long-standing Goodwill Ambassador for UNICEF, will focus mainly on the issue of 'stunting', which can lead to brain damage.
"Stunting - when children don't get the right nutrients in the first 1,000 days of life - is the hidden crisis stopping millions of children around the world reaching their potential. It's irreversible. It means children get trapped in lives of poverty," the father-of-four said.
"During the coming weeks all eyes will be on London for the greatest show on earth. As a UNICEF Ambassador, I am asking the Prime Minister to use the global spotlight on our nation to make children around the world the real winners of these Games."
Beckham was part of the committee that brought the iconic sporting event to London, and will be involved in the opening ceremony on Friday (July 27), but will not be taking part in the Olympic football after being overlooked by Team GB coach Stuart Pearce.
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