The research, carried out to mark World Friendship Day on Monday, also revealed that one in five do not even know how to write a letter.
Odette Brooks, founder of Leaps and Bounds Educational Services told Premier she's not surprised by the results, but it's still saddening.
"I think we live in an age where speed is king so we want communication to have a sense of brevity," she said.
"Young people now, they're fully engaged in text messaging as their main form of written communication. The problem with that is the quality is compromised."
World Vision uses letter writing as a way for families to build lasting friendships with the children they sponsor.
Lauren Vail, children's communications officer at World Vision UK said it has many benefits.
"The education which sponsored children get is often poor," she said.
"Letter writing helps these children develop their literacy and communication skills. Knowing that what you say is important to someone far away has a powerful impact on a child's confidence."
Brooks told Premier that writing letters should not be viewed as a thing of the past.
"Letter-writing does have its relevance today," she added.
"It's not some sort of archaic thing from the past. That's why World Vision's pen pal initiative is brilliant, because young people see letter writing is a brilliant way of keeping in touch with each other and expressing our ideas in a much more thoughtful way."
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