Spanish side Malaga have been banned from European competition for one season due to outstanding debts, but the club have stated that they will appeal the 'disproportionate and unjustified' decision.
The club has also been threatened with a further year's European ban by UEFA unless they prove they have no debts to other clubs, players or the tax authorities.
Malaga are currently fourth in the Primera Division and will face FC Porto in the last-16 of the Champions League but have had huge struggles with financial problems.
"The club [Malaga] is excluded from participating in the next UEFA club competitions for which it would otherwise qualify for in the next four seasons." - UEFA
The ban will be imposed if the club qualified for the Champions League or Europa League during any of the next four seasons.
UEFA says it will impose the additional ban unless Malaga provides the proof it has cleared its debts of 'overdue payables' by 31 March. It has also fined the club €300,000.
A UEFA statement said: "UEFA's club financial control body has taken its first decisions due to the presence of significant overdue payables.
"The club [Malaga] is excluded from participating in the next UEFA club competitions for which it would otherwise qualify for in the next four seasons."
Five other clubs face similar one-year bans during any of the next three seasons unless they can convince UEFA they have cleared the stipulated debts. They are Hadjuk Split and Osijek from Croatia, Rapid Bucharest and Dinamo Bucharest from Romania, and Partizan Belgrade from Serbia.
Malaga, owned by the Qatari al-Thani family, have vowed to challenge UEFA's decision.
A club statement said: "Malaga Club de Futbol wishes to communicate its total disagreement with today's UEFA decision.
"The measures taken against the club are absolutely disproportionate and unjustified given the club's situation. We consider that the club is being punished unfairly and used as an example to others.
"Given the total and absolute indignation and consternation on the part of the club, Malaga CF wishes to state that it will work energetically and without rest to achieve justice, using all available necessary means.
"Malaga CF wishes to add that it does not understand, and considers totally incomprehensible and abusive, that after having received this judgement it must now wait an unknown period of time to know the evidence upon which it was taken."