Everton are considering legal action against Jose Mourinho unless the Chelsea boss retracts his attack on England striker Andrew Johnson.
The Merseysiders are furious with Mourinho's implication that Johnson dived during Chelsea's dramatic 3-2 victory at Goodison Park on Sunday after a challenge by Khalid Boulahrouz.
Johnson has been under scrutiny this season with Arsenal boss Arsene Wenger and Sheffield United chief Neil Warnock commenting on him going to ground.
But Everton now believe that Mourinho has gone too far by claiming that Johnson is untrustworthy and that the Portuguese coach's post-match comments could be defamatory.
Mourinho branded Johnson 'a dangerous kind of opponent' and claimed he was 'not fair'.
'You cannot trust him,' he added. 'A great player but too much of that.'
Everton have today taken legal advice over whether Mourinho could have slandered the former Crystal Palace striker, and have issued a joint statement with Johnson's agent Anthony McFarlane calling for a retraction while asking football authorities to intervene in the growing row.
Everton are unwilling to comment further publicly as they wait for FA and Premier League action as well as a response from Chelsea and Mourinho.
Everton have brushed aside previous claims over on Johnson, but this time feel 'enough is enough' and they must now defend their player.
Sources at the club believe that this latest attack by a Premiership manager is damaging the value of their asset, is offensive and having an effect on the player's mental state.
Johnson has not scored for 13 games as a season of debate over whether he dives or not has grown into the current crisis.
Everton's statement implored Mourinho to retract his comments while asking for football authorities to look at the words used.
Everton issued the statement on the club's website on behalf of the club and Johnson's BaseSoccer representative Anthony McFarlane, which read: 'In the wake of Sunday's Premiership game against Chelsea at Goodison Park we wish to jointly condemn the post-match comments of Jose Mourinho relating to Andrew Johnson.
'To publicly question the integrity of a player of Andrew's professionalism and honesty is not only wholly unacceptable and quite possibly defamatory but also, in our opinion, highly damaging for both club and player.
'We would urge the footballing authorities to look closely at Mr Mourinho's comments and then, perhaps, seek a formal explanation.
'Both Everton Football Club and Andrew Johnson have always believed in the virtues of fair play and we would ask Mr Mourinho to immediately retract his allegations.'
In his post-match interviews, Mourinho implied Johnson had dived to win a penalty although television replays suggested he had received a shove in the back from Boulahrouz before going to ground.
Everton boss David Moyes has defended Johnson saying: 'In my eyes the referee gave what he saw. It shows that even such a good coach as Jose Mourinho gets it wrong and doesn't choose the right words at the right moment.
'It was only a few weeks ago that their goalkeeper Petr Cech got stood on at Reading. In this instance our player jumps over the goalkeeper to avoid injuring him and he gets criticised for that.
'You have to decide who you think is making the rules up.'
A Premier League spokesman said: 'This is a matter for the FA and we would only get involved if it was a direct dispute between the clubs. Otherwise it is a disciplinary situation for the FA.'
An FA spokesman claimed they would not comment until they received an official complaint from Everton.
Phil Neville has also warned Mourinho to keep his nose out of Everton's business.
Neville has rounded on Mourinho, blaming the likes of the Chelsea manager and Arsenal counterpart Arsene Wenger - who was also critical of Johnson earlier this season - for getting his team-mate a bad name.
'Jose Mourinho has no right to say things like that,' said Neville. 'It wasn't a case of cheating at all. The reason why Andrew Johnson is not getting penalties at the moment is because people like Arsene Wenger and Jose Mourinho are coming out and having a go at our players.
'It is nothing to do with him. He should leave everything that is concerned to Everton FC to our manager and our chairman.'
Including yesterday's incident, which admittedly Moyes said should not have resulted in an Everton penalty, Neville is convinced Johnson has been denied four spot-kicks this season alone.
'He was pushed over at Fulham, pushed over at Blackburn, pushed over against Arsenal and again yesterday,' said the Toffees' skipper. 'Believe me, Andrew Johnson does not go down easily in the area but on none of those occasions did he get a penalty.
'Maybe he (Mourinho) needs to be sent a video of this and have a look at himself in the mirror.'
Of more concern to the Everton camp just now is Johnson's 11-match scoring drought since he netted his sixth of the season in the home draw with Manchester City on September 30.
After such an explosive start to the campaign, the former Crystal Palace star is now struggling for chances.
However, his link up with 18-year-old rookie Victor Anichebe against Chelsea was encouraging and Neville has nothing but admiration for Johnson's contribution to Everton's overall team play.
'Andy has gone a few games without scoring but you can see from his effort and quality it has not affected him,' said Neville, who must now serve a one-match suspension after picking up his fifth booking of the campaign.
'Goalscorers thrive on goals and I am sure he would tell you he would love to score.
'But his overall play was fantastic and he terrorised the Chelsea back four, making runs behind and creating a lot of space for Victor.'