Click here to read The Voices Live
About 80 Britons died in the attacks on the World Trade Center in New York, and numbers remain inexact as only four people have been positively identified.
The specially commissioned poem, The Voices Live, pays tribute to the dead and their family and friends.
Nearly 4,000 people were killed in total in the attacks on New York and the Pentagon, in Washington, and in another hijack that ended with the plane crashing in Pennsylvania.
Motion, who was appointed in 1999, aims to convince people that poetry is, and should be considered, part of their everyday lives.
Public concern
His role includes marking special state events with a poem, and previous works include the marriage of Prince Edward to Sophie Rhys Jones and the Queen Mother's 100th birthday celebrations
He has also written verse to mark events and causes of more personal public concern, such as the Paddington rail disaster and the charity Childline.
Motion's work involves working with the government to promote his ethos at grass roots levels among the young.
The government has, he says, been "very receptive" to his wish to see poetry protected and promoted in the National Curriculum.