Poole Town have been docked three points for fielding a suspended player in the Calor League.
The Dorset club are one of Bideford's main rivals for a play-off place in the Premier Division.
Poole inadvertently played Sam Clarke in the win against Redditch United in December when he should have been serving a one-match ban.
They have been fined £250 and deducted three points.
Bideford, in fifth, have 13 games to play and are hoping to hold on to the final play-off place.
They look set to come under pressure from Poole and Stourbride who can move above them by winning their games in hand.