Wigan chairman Dave Whelan has written to the Premier League asking for proof that Argentine striker Carlos Tevez is eligible to play for West Ham.
Tevez played a key role in West Ham's win over Wigan
West Ham say they have ripped up a contract they entered into with a third-party company which breached Premier League rules.
But Whelan said: "Surely the contract can only be terminated by both parties?
"Could we see concrete evidence of this and was the termination complete before 28 April when Tevez faced Wigan?"
Wigan lost that game 3-0, with Tevez playing a key role in a victory which boosted the Hammers' chances of survival and put the Latics further in jeopardy.
Are you being told lies again?
Dave Whelan's letter to the Premier League
West Ham were told the day before the match that they had been fined £5.5m for breaching rules over the signings of Tevez and Javier Mascherano but had not been docked points.
That prompted an angry reponse from the Hammers' relegation rivals, who threatened legal action over the decision.
The Premier League says any action against the decision would be futile, because all 20 clubs agreed to the disciplinary system in place.
However, West Ham were also warned that Tevez's registration could be cancelled unless the third-party agreement was anulled.
West Ham say they did that, but there appears to be some doubt over whether Kia Joorabchian, who part-owns one of the third party companies and played a key role in bringing Tevez and Javier Mascherano to West Ham, agreed.
In his letter, Whelan refers to a meeting between himself, Premier League chief executive Richard Scudamore, Wigan chief executive Brenda Spencer and manager Paul Jewell.
"At that meeting, you clearly stated the then West Ham chief executive Paul Aldridge looked you square in the eye and told you blatant lies regarding the contracts of the Argentinian players. Are you being told lies again?
"Could we and the rest of the Premier League please see concrete evidence - ie written confirmation this contract had been cancelled by both parties."