The 42-year-old Scot was sacked by the Welsh club in December and just when he appeared set to return to football by snaring the Crystal Palace job, news broke earlier this week that the FA were investigating a dossier compiled by Cardiff detailing Mackay's misconduct.
The dossier revealed several text messages of racist, sexist, homophobic and anti-semitic nature exchanged with his former assistant manager Iain Moody, who subsequently stepped down as Palace sporting director on Thursday.
On Friday evening, Mackay offered a full apology during an exclusive interview with Sky Sports News HQ.
He said: "Obviously the texts are things that I absolutely have to explain by talking to you today. Out of 10,000 text messages in and out of someone's phone I sent three that, looking at them, are completely unacceptable and inappropriate. For that, and for any offence they caused, I sincerely apologise.
"It's something I did and there's no excuse for that. I did it in a period where I was under immense pressure and stress in terms of the relationships that were not going too well at my football club. Once again, that doesn't actually excuse anything. It was unacceptable for a manager.
"I'm a human being and I made a mistake.
"I suppose I would humbly ask people to ask themselves that if their own phone was taken and every text was scrutinised, if there'd be a certain amount of embarrassing texts for everyone.
"It was something that was unacceptable but I've been in a multicultural environment for 20 years. I love British football and I'm no racist, no sexist, no homophobe and no anti-semite. The people that know me, know that. I know it's the people that don't know me that I've got to convince of that.
"I'm sincerely apologetic for those three texts and for any offence that was taken. It was wrong and it's something that isn't in my character. Anyone that knows me knows it's a mistake that I've made. I know it's not what people see of me when they meet me and talk to me.
"It was someone else's phone that had a vast array of 10,000 texts lifted from it. I received some but the three I've sent that are in question, I'm accountable for.
"I've been speaking to my union about the equality and diversity training and it's something that I'll be going forward with. Organisations like Kick It Out and Stonewall too. I know I have to prove to people who don't know me that I'm someone who's passionate about football and this is not who I am."
Cardiff have also called into question the transfer dealings under Mackay with various payments to agents and lawyers under scrutiny but the former Scotland defender is adamant that all the comings and goings during his reign were above board.
He added: "There's an FA investigation going on at the moment and I'm 100% confident that the investigation will show I am guilty of absolutely no wrongdoing in terms of transfers at the club. Secondly, I signed a non-disclosure agreement with Mehmet Dalman at Cardiff City and I have to hold my end of the bargain up.
"I have to comply with the FA in this investigation to the letter of the law. Anything they need from me, I'll be available here. What I've done is made a mistake. I sincerely apologise for that. These are testing times but I've got values and resilience. I will come back from this.
"I hope I'm given the opportunity. The last 20 years, I've worked with huge diversity, different ethnicities, colours and creeds. Many people have had dealings with me in football."
In the wake of the publication of the text messages, the League Managers' Association issued a statement on Mackay's behalf that attempted to excuse the messages as 'banter' - only to back down under pressure and apologise for the wording of their press release.
Mackay, however, rejects claims that the handling of the situation should lead to the sacking of LMA chief Richard Bevan.
He said: "I've certainly never used the word 'banter' to describe what it was but I think the overall statement was very accurate. I agree that word is wrong and they've tried to correct that today.
"I think a lot of that statement was factual and there were various parts of it that there's absolutely contrition on my part. The use of that word was wrong, but the LMA have a long-standing reputation in the game which is very good. Every manager in the country backs the good work the LMA do for this country in all walks of life.
"They made a mistake and they changed it. I don't think they meant any offence. Without a doubt, 'banter' wasn't a word I used. I don't (think Richard Bevan should be sacked).
"The amount of work they've done in grass roots football, you'll find he's been someone who's made a lot of good decisions and a lot of good work for the country in terms of football."