West Ham have denied making "inconsistent" statements about the status of striker Carlos Tevez, whose move to Manchester United is in doubt.
Tevez has been at West Ham since August 2006
Tevez's adviser, Kia Joorabchian, says the Hammers made "promises and assurances" about the 23-year-old Argentine which they have not acted on.
But West Ham insist every document regarding them and Tevez has already been scrutinised by the Premier League.
Fifa is to look at the deal after West Ham and United asked them to intervene.
The striker's move to Old Trafford is in danger of breaking down because the two clubs cannot agree a way forward.
Tevez has been in Manchester since Tuesday night but West Ham refused permission for him to have a medical at Old Trafford.
Over the last six months West Ham have made repeated promises and assurances which they have not acted upon or performed. It is now time for these inconsistencies to be brought to an end
The Hammers insist they are still waiting to receive an offer for Tevez.
And the Premier League says a deal must be done between United and West Ham but not Joorabchian, who claims to own Tevez's economic rights.
A special 'dispute resolution chamber' will be set up by Fifa, possibly within a fortnight, to effectively determine who currently owns Tevez - West Ham or Joorabchian.
West Ham were only allowed to keep playing Tevez last season after assuring the Premier League all third-party clauses in the player's contract had been severed.
Joorabchian issued a statement late on Wednesday on behalf of his company Media Sports Investments (MSI), which read: "West Ham have consistently provided private assurances while at the same time making contrary statements to the public at large.
"We can no longer allow these inconsistencies to continue unaddressed.
"We wish to make clear that at all times it has been our intention to find an amicable solution and Carlos Tevez has, at no time, acted improperly in relation to his move to Manchester United as he was given permission via his representatives to talk to other clubs to reach an amicable agreement.
"Over the last six months West Ham have made repeated promises and assurances which they have not acted upon or performed. It is now time for these inconsistencies to be brought to an end.
"We see no alternative but to bring the true circumstances to the attention if a higher authority to aid a rapid conclusion to this issue."
But West Ham responded on Thursday with a strongly-worded statement of their own, saying: "We totally reject the latest outburst and threats issued in the name of Kia Joorabchian in relation to the situation regarding Carlos Tevez.
"We will not be drawn into this form of public mudslinging but these latest statements cannot go unanswered.
"Mr Joorabchian entered into agreements with the previous regime at West Ham at a time in which he was attempting to take over the club. Those arrangements, since terminated by West Ham, led the club into serious disciplinary difficulties for which the club has paid a heavy price.
"It is absolutely clear that the only contract relating to Carlos Tevez recognised by West Ham and the Premier League is the player's four-year contract which runs until June 2010.
"All other arrangements were terminated by West Ham on 27 April 2007 and no legal challenge to that termination has occurred.
"West Ham can also confirm that all documentation regarding the club and Carlos Tevez has already been submitted to the Premier League and fully scrutinised by them. We have ensured full disclosure."
The Hammers have tried to persuade Tevez to stay at Upton Park but insist they will be happy to accept Fifa's decision on the matter.
Public threats and accusations are irrelevant, let Fifa decide and West Ham will accept that judgement whatever the outcome
The statement added: "The club has in recent weeks made every effort to keep Carlos Tevez at West Ham and indeed offered significantly improved terms and conditions to the player, which were not accepted.
"However a transfer of a properly registered player cannot occur without agreement between two clubs and the Premier League.
"Without such an agreement we believe that it is in the interest of all parties to resolve this issue as quickly as possible through the procedures laid down by Fifa.
"Public threats and accusations are irrelevant, let Fifa decide and West Ham will accept that judgement whatever the outcome. The time has come to settle this matter in a way which will allow everyone concerned to move on."