Nottingham Forest have written to both Tottenham and Morgan Gibbs-White's agent, threatening legal action over what they believe was an unlawful approach for the player and a breach of confidentiality laid out in the player's contract.
Sky Sports News has been told the letters put both parties "on legal notice", reminding them of their obligations and spelling out how Forest believe both Spurs and Gibbs-White's representatives have breached Premier League rules and the terms of the player's contract.
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Tottenham have not commented publicly, but it is understood they believe they have done nothing wrong, and they retain an interest in signing the midfielder after being unsuccessful with a £60m bid.
Far from backing down on this issue, Forest have made it clear that even though they have taken no punitive action so far, they are prepared to do so in the future - both via the Premier League and the law courts.
Sky Sports News' Rob Dorsett answers the key questions around the transfer saga...
What are the rules on approaching players?
Even though it is relatively commonplace for clubs to sound out their would-be transfer targets in advance, 'tapping up' (or any meaningful negotiation) is banned under the Premier League rules.
Rule T.3 in the Premier League handbook says a buying club must get written permission from the selling club before approaching any player, or they face disciplinary action.
"Any Club which… makes an approach either directly or indirectly to a Contract Player except as permitted by either Rule T.1.2 or Rule T.2 shall be in breach of these Rules and may be dealt with under the provisions of Section W (Disciplinary) of these Rules."
What is the contract confidentiality dispute?
Concerning Gibbs-White's current contract, legally there is a conflict between the rights of the employer and those of the employee.
Forest have a contractual agreement for the terms of Gibbs-White's contract - and specifically the level of his release clause - to be kept confidential, so if that has been breached, they have a legal case.
Conversely, Gibbs-White has a contractual agreement that if another club is prepared to pay a certain transfer fee, he can leave the City Ground. He has a potential legal claim there, too.
Neither side wants to see this end up in the courts but both sides have that as a possibility in the background.
What does Gibbs-White want to do?
Sky Sports News has learned that Forest have been trying for almost 12 months to open negotiations with Gibbs-White over a new and improved contract at the City Ground, but he has refused to engage in those talks.
Forest are prepared to give him a huge pay rise, in exchange for the removal of the release clause, which would make him one of, if not the, biggest earner at the club.
From Forest's point of view, Gibbs-White's refusal to discuss a new contract shows he doesn't have a long-term commitment to Forest.
So what's next?
The result is the current stalemate. If Gibbs-White really wants to join Tottenham, it may be that he has to bring legal action against Forest - claiming a breach of contract - to try to force a move.
There is no indication that he is prepared to do that currently, and in fact he returned to pre-season training yesterday as scheduled, with the rest of Forest's international players.
Alternatively, it could be that Spurs are prepared to increase their offer for the player, and pay an amount above his release clause, to try to placate Forest and re-open lines of communication.
Again, there is no indication at this stage that Spurs are prepared to do that, and there is no dialogue between the two clubs.
It is also possible that another club takes advantage of the impasse, and comes in with a separate offer for the player. Manchester City showed an interest in Gibbs-White earlier in the window but have not pursued that interest.
Neither Forest nor Spurs have commented on these latest developments.
How difficult is this situation for Forest?
It is a very sensitive one. They don't want arguably their best player to be unhappy, but they also don't want to be viewed as a 'selling club' or one that is lacking ambition.
Following the departure of Anthony Elanga to Newcastle, were Gibbs-White to leave too, Forest will have lost two of their best players - albeit by earning £115m - before the season starts.
Marinakis will strongly defend his own reputation and the standing of his football club, although the presence of the release clause is of real concern and ultimately means Forest don't have control over the future of one of their key assets.
Marinakis and Daniel Levy, the Tottenham chairman, are among the toughest negotiators in the Premier League and neither is likely to back down.
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