Haywards Heath Town will appeal a misconduct charge which could cost them the Southern Combination Football League Premier Division title and promotion to the Isthmian League.
Heath celebrated winning the league last week after beating Horsham YMCA 7-1 in the final game of the season.
The win meant they finished four points ahead of rivals Shoreham.
But on the day there was no trophy presentation as an investigation was carried out by the Sussex and London FAs.
A statement released this week by the Sussex FA said: “The Sussex County FA in conjunction with London FA, have carried out a full investigation into the allegation.
“As a result both the player and the club have been charged with misconduct and we are awaiting their responses to these charges.”
Haywards Heath Town secretary Mark Russ said the club will contest the charge as they believe they have done nothing wrong.
He told Middy Sport: “We have been charged with playing the ineligible player. And will now obviously contest that.
“We feel, as I said last week, we have done nothing wrong.
“We are totally in limbo and as when a decision is made we can prepare for next season.
“We are going to now answer the charge and put in our appeal and then we wait to get the hearing date then go from there.”