Malky Mackay and Iain Moody will not face any disciplinary action over controversial text messages sent while the pair were working at Cardiff, the Football Association has announced.
The FA announced in August last year that it was investigating after Cardiff sent a dossier containing private messages between Mackay, the club's former manager, and Moody, the club's former head of recruitment, between June 2011 and March 2014.
The Daily Mail had published details of the messages, which Mackay said were "regrettable," although he also expressed concern about "seriously inaccurate and misleading reports" in the media.
The FA has now said that, following a "thorough and detailed investigation" that lasted almost a year, it will not bring charges against either Mackay or Moody but said there had been discussions with both over their conduct.
A statement read: "To date, The FA's policy in cases such as this has been to not bring charges in respect of private communications sent with a legitimate expectation of privacy.
"The FA's investigation looked at all aspects of the communications, including the context in which the communications were sent. The evidence was then reviewed by a QC with particular expertise in sports' disciplinary proceedings and employment law.
"Having assessed the evidence, and in light of the finding that the communications were sent with a legitimate expectation of privacy, The FA will not be taking disciplinary action against Iain Moody and Malky Mackay in connection with the content of those messages.
"However, The FA has spoken to both Iain Moody and Malky Mackay about the inappropriateness of terms used in the messages. Both individuals have acknowledged that such terms are not acceptable. Mr Mackay has also voluntarily undertaken equality and diversity training."
Former Cardiff player Ibrahim Farah had reportedly accused Mackay of racism after the controversy emerged, while the reported text messages had referred to ethnicity in discussions on player recruitment.
However, the FA statement said it had also investigated whether there had been any evidence of discriminatory behaviour in the pair's work at Cardiff and nothing had yet come to light.
The statement added: "The FA has pursued every lead and encouraged anybody who wanted to provide information or evidence to do so. Malky Mackay and Iain Moody have been interviewed at length and 27 potential witnesses, based in the UK and overseas, have been spoken to.
"All of the information and evidence gathered during this process has been carefully assessed, with the assistance of a QC. At this stage no disciplinary charges will be brought against either Malky Mackay or Iain Moody in respect of their conduct whilst they were employed by Cardiff City FC.
"The FA has reached its decisions based on the information and evidence currently available to it. Should more information or evidence come to light then The FA reserves the right to bring disciplinary action as appropriate."
Explaining the length of the investigation, the FA added: "The investigation has been lengthened considerably due to serious concerns about the circumstances in which particular evidence provided to The FA had been given and the reliability and completeness of that evidence.
"The FA reserves the right to open further investigations if deemed appropriate. No further comment will be made in this respect."
Mackay, who had been sacked by Cardiff in December 2013, returned to management in November in a brief stint with Wigan, which had brought criticism from Bluebirds owner Vincent Tan.
Moody, who had been appointed a role as sporting director at Crystal Palace in November 2013 after being sacked by Cardiff the previous month, resigned his post at Selhurst Park when the text messages came to light.
Anti-racism campaign group Kick it Out, which seeks to tackle racism and discrimination within football, has hit out at the move.
- Kick It Out (@kickitout) July 16, 2015
A statement said: "Kick It Out is of the view that The Football Association has damaged its own credibility and anti-discrimination policies by taking the decision not to charge former Cardiff City and Wigan Athletic manager Malky Mackay and Iain Moody, a former employee of Cardiff and Crystal Palace, for alleged racist, anti-Semitic, sexist and homophobic comments revealed by the Daily Mail in August 2014.
"The FA has continued to maintain a distinction between public and private communications.
"These messages were exchanged via work phones and emails, and when they did eventually emerge into the public domain, it became clear to many people that such held and expressed views had brought the game into disrepute unless dealt with effectively and expeditiously.
"Once the messages were disclosed, there was a clear public interest in action being taken. Mackay and Moody admitted their involvement and this is clearly an abrogation of responsibility on the part of the FA. The review currently being undertaken by the FA of its unwritten policy on dealing with 'private communication' is lamentably late in the day.
"It is Kick It Out's view that the FA needed to take a strong position to help prove football's 'zero-tolerance' approach towards discriminatory practices.
"Instead, we have another example of the status quo being reinforced, and discriminatory practices being allowed to flourish in 'no-go' areas such as within the exclusivity of boardrooms, training grounds and dressing rooms, and via private communication networks. "How can anybody truly challenge discrimination and prejudiced attitudes in football with confidence now?
"The apparent reluctance to punish comments and behaviour considered as 'banter' or 'light-hearted culture' within these settings is entirely damaging. It is an insult to those affected by discrimination and offers the prospect of further victimisation if they are to take a stand and confront it.
"Too many people capable of discriminating operate in private, and they are acutely aware of what will land them in trouble if they act this way in the presence of others. The outcome of the FA's investigation in this case, after such an exhaustive process lasting nearly a whole year, will empower these individuals.
"The case symbolised a serious challenge to the leadership of football and sadly the FA has missed a key opportunity to send out a message to individuals who use private communications to express such unacceptable views."