Birmingham have recalled young midfielder Charlee Adams from his loan spell with Vanarama Conference side Lincoln.
Premier League: Jose Mourinho says captain John Terry will receive a contract extension to stay at Chelsea beyond the end of this season.
Manager Jose Mourinho has said he can guarantee skipper John Terry "will be a Chelsea player next season".
Hackett, 29, made 145 appearances for the Lions, scoring five goals, since joining from Hearts in 2006.
However, he slipped out of the first-team picture this season and ended the campaign on loan at Wycombe.
Former Leicester and Watford full-back Stewart, 30, endured an injury-hit season since he signed last summer and managed just seven appearances.
Youngsters Jake Gallagher and Conor McLaren have also been released.