Birmingham have announced the resignation of their chief executive Xuandong Ren.
Ren, appointed to the board at St Andrew's by the club's owners Trillion Trophy Asia in the summer of 2017, has been the subject of increasing fan protests this season.
A statement on Birmingham's official website said: "Chief executive officer, Xuandong Ren, has resigned from his position at the club with immediate effect.
"The Board would like to place on record their sincere thanks for his service and contribution. The club will be making no further comment at this time."
Birmingham issued a statement on Saturday in response to banners that had been put up by a Blues fans' protest group in Blackburn town centre before their final game of the season at Ewood Park.
City claimed one of the banners was "undoubtedly racist" and that it was "unacceptable".
Birmingham finished 18th in the Sky Bet Championship and Ren has come under increasing pressure from supporters to step down.
Fans demonstrated against owners TTA and Ren, known informally as Dong, in particular before City's 3-0 home defeat to Bristol City in March and there have been further protests.
Former Charlton boss Lee Bowyer was announced as Karanka's successor soon after and steered City clear of relegation as they finished nine points above the bottom three after losing their last two matches.