Monaco have accused some of Europe’s top clubs of making illegal approaches for teenage striker Kylian Mbappe.
The Ligue 1 club said in a statement that “important European clubs” have made contact with the 18-year-old France forward without permission.
Monaco may ask world governing body Fifa and the French league to consider disciplinary action.
BBC Sport understands Manchester City are the only English club accused. They have refused to comment officially.
A City source, however, told BBC Sport the two clubs developed a positive relationship over their two Champions League meetings last season.
It is understood negotiations over the sale of Bernardo Silva to City for £43m earlier in the summer were positive, and the ongoing dialogue over £50m-rated full-back Benjamin Mendy has also been cordial.
The source added they did not believe City had conducted themselves in such a way that would breach the trust that exists between the two clubs.
Arsenal have also been strongly linked with Mbappe, and Monaco reportedly rejected an £87m bid for the France international in June.
Mbappe scored 26 goals in 44 appearances for Monaco last season as they won Ligue 1 for the first time in 17 years and reached the semi-finals of the Champions League.
Monaco claim clubs have breached regulations of both Fifa and the Ligue de Football Professionnel.
Fifa rules state: “A club intending to conclude a contract with a professional must inform the player’s current club in writing before entering into negotiations with him.”