The five-day event, which was hosted by the ACC Liverpool between 25 and 29 September, was attended by 11,000 delegates and was estimated to have contributed £15m to the city's economy.
Milliband said: "Liverpool has been a fantastic host city and I would like to thank all the people and agencies involved in making our conference such a great success.
"Listening to people has always been at the heart of Labour Party conference and by holding conference in Liverpool many people have experienced conference for the first time. The city and its venues have been a fantastic back drop for a very successful conference."
In addition to the main event at the ACC, home to the BT Convention Centre and Echo Arena, around 500 fringe meetings took place at venues across the city.
Bob Prattey, ACC Liverpool's chief executive, said: "We are proud to have welcomed the Labour Party Conference to the city and to ACC Liverpool.
"The conference has enabled us to showcase everything the city and our world-class venue has to offer, not least the talent of our team here at ACC Liverpool, the expertise of our partners across the city and the warm welcome that the people of Liverpool have once again provided."