In the English Premier League, if any team deliberately tries to lose a game to give the opposition more points that could possibly damage the league position of a third team, say by fielding a weakened side or in extreme case score own goals, is there any penalty they could face for such action?
Also, I heard few years back that relegation some candidate threatened to report Chelsea to FA because they fielded a weakened side with young players against their relegation rivals at the end of the season game.
Is there any particular criteria set by FA to determine just what constitutes a weakened side in such a case, since the strength of a team is very subjective? Secondly has there ever been any action taken for such an incident in past?
EDIT: (Could find an example for EPL but here's a hypothetical example for CL group stage where losing is beneficial)
In the final two matches Roma play Celtic and Barcelona play Shaktar. Barcelona had a poor run in previous five games due to injury to key players and silly red cards. Assuming that Barcelona can beat Shaktar in the final game, it makes sense for Roma to lose to Celtic deliberately to make them qualify instead of Barcelona, so that they wouldn't have to face a full strength Barcelona later in the group stages when all their key players have recovered.