Lyon have blamed West Ham for the collapse of a loan deal for Said Benrahma and accused the Hammers of “a profound lack of respect”.
The Algerian winger, 28, had been set to move on loan to the French side on transfer deadline day.
But the Hammers confirmed in the early hours of Friday that a move was “unable to be completed before 11pm”.
Elsewhere, Real Betis hope Pablo Fornals’ move will be ratified after a “computer problem” on West Ham’s side.
After the collapse of Benrahma’s move, Lyon accused West Ham of not taking the required action to complete the deal.
In a strongly worded statement, the Ligue 1 side criticised the Premier League side’s “incomprehensible behaviour”, adding: “Olympique Lyonnais deeply regrets this situation and this decision, demonstrating a profound lack of respect on the part of West Ham towards the institution and the player.”
Lyon, who are owned by Crystal Palace co-owner John Textor’s Eagle Football Holdings, said they also “reserve the right to undertake all appropriate procedures necessary to validate the transaction at a later date, and to hold West Ham responsible if necessary”.
Asked about why Benrahma’s move collapsed, Hammers manager David Moyes said on Friday: “It looks like there have been some problems with the paperwork at the last minute. But I only learned about it when I came off the pitch late last night.”
Benrahma joined West Ham from Brentford in October 2020 and his current deal runs to 2026.
He started last season’s Europa Conference League final against Fiorentina and scored the opening goal from the penalty spot in West Ham’s 2-1 win.
However, the attacker has failed to find the net in 22 appearances this season and was sent off in the FA Cup replay defeat at Bristol City on 16 January. Benrahma was controversially left out of Algeria’s squad for the Africa Cup of Nations tournament.