The League Managers Association confirmed Thursday that former Cardiff manager Malky Mackay sent text messages to a colleague at the Welsh club that were "disrespectful of other cultures."
But the LMA provoked outrage by adding that the exchanges occurred during "friendly text-message banter" and that Mackay was just "letting off steam to a friend."
"The LMA apologizes for some of its wording ... which was inappropriate and has been perceived to trivialize matters of a racist, sexist or homophobic nature," the organization said in a second statement. "That was certainly not our intention.
"It is beyond argument that any comments that are discriminatory, even used in private, are totally unacceptable."
Cardiff reacted hours later, saying the club found it "entirely reprehensible that the LMA should itself put out a statement which seeks to dismiss deeply offensive racist comments as'friendly banter.'"
Cardiff called for the resignation of the LMA's chief executive, Richard Bevan, saying his position is "untenable."
The text-message controversy involving Mackay and Iain Moody, a former colleague at Cardiff, is being investigated by the English Football Association after the governing body received a dossier from the Welsh club containing the inappropriate texts allegedly sent by the two men.
Messages of a sexist and homophobic nature were also in the dossier, according to sections of the British press.
Mackay was fired by Cardiff in December after falling out with the club's Malaysian owner Vincent Tan, and this latest scandal stopped his chances of taking over as manager of Crystal Palace.
Mackay apologized in person Friday, saying in an interview on Sky Sports: "Looking at them (the offending text messages), they are completely unacceptable and inappropriate ... (but) I'm no racist, no sexist, no homophobe."
He added that he will put himself on an equality and diversity course.