The League Managers' Association have revealed Celtic are yet to reach a settlement with sacked boss Tony Mowbray and his staff.
Mowbray and his assistants Mark Venus and Peter Grant were axed at the end of March after less than a year in charge following a string of poor results.
The LMA are representing Mowbray and Grant in negotiations with the club over a pay-off, which reportedly could be as much as £1.4million, although the precise terms of Mowbray's contract are unclear.
While most settlements are reached within three weeks, the association says Celtic are still to settle in this case.
LMA chief executive Richard Bevan told the News of the World: "We're acting on behalf of Tony Mowbray and Peter Grant on this issue and are dealing with Celtic. Technically, they are currently on gardening leave from the club.
"In the majority of cases, settlements are reached for members of coaching staff within two to three weeks. You would need to speak to Celtic about their motives in the delay.
"The reason we're representing Tony and Peter is that they are members of the LMA.
"It isn't the case that clubs have to have settled with previous employees before they appoint new managers - every contract is different and I can't comment on individual ones."
Meanwhile, young Celtic midfielder Simon Ferry insists he would be happy to turn his on-loan move to Swindon into a permanent deal next year if the clubs can agree a deal.
The 22-year-old, who has not made a single first-team appearance for the Hoops, told Scotland on Sunday: "To be honest, if Swindon want to keep me then I'd be more than happy to stay, especially if the new Celtic manager comes in and tells me I just have to fight for the chance to get a game.
"If a manager like Danny Wilson wants to buy me then I would rather come back to Swindon and play for him and play somewhere I'm wanted.
"I can't really see myself getting a chance at Celtic and I don't think it would matter who the new manager is because there are so many players ahead of me there, so it would be a waste of time going back really."