Steve Cotterill: Birmingham City sack manager after five league defeats in a row
Blues lost 2-1 at Nottingham Forest on Saturday to remain two points adrift of safety in 22nd with 11 games remaining.
Former Bristol City boss Cotterill, who was appointed manager in September after Harry Redknapp's dismissal, won just six league games out of 24.
Birmingham are now looking for a fifth manager in 16 months since Gary Rowett was sacked in December 2016.
Speculation had surrounded Cotterill's future at St Andrew's, with former Leeds United and Middlesbrough manager Garry Monk linked with the job.
Cotterill, who this week met with Hong Kong-based chairman Zhao Wenqing, admitted his frustration about the rumours after the defeat at the City Ground.
"If that's been going on behind my back, it's best for them to get on with it," he told BBC WM 95.6.
"What I've learned is you can't judge other people by your own standards," he added. "I've stayed professional throughout, worked extremely hard in the time I've been at this football club."
Birmingham, who are the lowest scorers in Championship this season with 23 goals from 35 games, are next in action on Tuesday when they are home against seventh-placed Middlesbrough.