Both David and Harvey had high profile careers that spanned four decades — winning Olympic and Championship medals for Great Britain.
David won individual Olympic bronzes in 1960 and 1968 and European championships in 1961, 1967 and 1969. He was voted BBC Sports Personality of the Year in 1960 and also won the King George V Gold Cup a record six times.
Harvey Smith won silver at four European championships and a bronze world championship medal.
“With both men having performed with such unswerving success for such a significant time, the depth of knowledge and insight that David and Harvey bring with them is insurmountable,” said a spokesman for BS.
The pair will have an advisory role, aiding World Class Showjumping Performance manager Rob Hoekstra.
“We will only move forward and continue to improve if we pull together as a team and embrace those who can make both a contribution and a difference,” said Mr Hoekstra.
“In David and Harvey accepting ambassadorial roles I feel we have just this. I feel fortunate to have both of these extraordinarily talented men supporting the British team in such a public way.”
Iain Graham, chief executive for BS added: “Under Rob Hoekstra’s guidance we have enjoyed a much improved performance at senior level with many new horse and rider combinations making their debut appearances with great promise.
“With Rob having the added support of such respected former riders as David and Harvey as international ambassadors, we are sure it can only reap further rewards and we would like to thank both of them for the enthusiasm with which they accept this role.”