Robert Hirst, category manager for dairy at Tesco, has left to join farmers' co-operative Milk Link in the newly created role of trading director.
He will be responsible for more than £220m worth of milk and ingredients sales. He will manage a team of five people, developing and implementing sales strategies for the milk and ingredients markets.
Hirst joins the board of Milk Link Holdings after 15 years at Tesco, where he was responsible for £1bn worth of dairy sales in his last post.
He said: "I am looking forward to bringing my experience in buying to a new role in what is one of the most progressive dairy businesses in the UK."
Barry Nicholls, chief executive of Milk Link, said: "Hirst brings a huge amount of pertinent experience to the role. His knowledge will be invaluable to us."