Raymond Verheijen has accused the Welsh FA of being "very disrespectful" for not inviting a former member of staff to Gary Speed's memorial match.
Wales assistant coach Verheijen has claimed team operations manager Adrian Davies has been "sacked" and "will not be at" Wales' game with Costa Rica.
But the Football Association of Wales insist Davies was employed on a match-to-match basis by Speed.
The FAW added Davies has been invited to the game in Cardiff on 29 February.
Verheijen's FAW future is uncertain as new boss Chris Coleman insisted "nothing is definite" if he continues in Wales' management team following a recent meeting between the two men in London.
Now the Dutchman, who has helped coach the Netherlands, Russia and South Korea at World Cups, has criticised his employers on a social networking site.
"I still can't believe the FAW has not invited Team Operations Manager Adrian Davies to be with the team at Memorial game. Very disrespectful," Verheijen told his Twitter site.
Wednesday's tweet came just two days after Verheijen said: "Just been told Team Operations Manager Adrian Davies been sacked & will not be with the team at Memorial Game of his friend Gary Speed."
But the FAW told BBC Sport: "Adrian Davies was appointed on a match-to-match basis by Gary Speed and was never contracted by the FAW.
"He has received tickets for the match along with hospitality."
Verheijen and Osian Roberts were Gary Speed's assistants before the death of the former Wales manager in November.
Verheijen has previously stated his Wales contract is until 2014 but Coleman is yet to confirm if he will remain part of his backroom staff.
Coleman has appointed former Wales and Fulham team-mate Kit Symons into his management team and Roberts will also remain in the Wales set-up.
Roberts and Verheijen are due to take charge of team affairs for the Gary Speed Memorial Match against Costa Rica at the Cardiff City Stadium as Wales will pay tribute to their former captain and most-capped outfield player.
But when asked about Verheijen's long-term role in the new Wales set-up, Coleman admitted: "Nothing is definite.
"We need to do this game for Gary and it is almost like everything is on standby as we all need to pay our respects to Gary.
"After that we can sit down and see where we are going forward."
Wales won four of their last five internationals before Speed's death and in the Fifa rankings in 2011 as they moved to 48th place from 113th in the world.
Verheijen advised the FAW only "need a figurehead who is willing to adapt to the current backroom staff and set-up" before Coleman's appointment "because everyone can see we that we have developed a winning formula."