Barcelona president Josep Maria Bartomeu claimed the club had been victims of "a great injustice'' after their appeal against a two-window transfer ban was dismissed by the Court of Arbitration for Sport on Tuesday.
The Catalan outfit turned to CAS in August after FIFA rejected their appeal to overturn the ban, which was imposed by world football's governing body in April due to concerns over the ''international transfer of minors.''
But their quest hit a further dead end on Tuesday morning, with the CAS ruling meaning they will be unable to sign any new players in 2015 -- much to the dismay of Bartomeu.
"A great injustice has been committed today: an injustice for Barca, for all the children and parents affected by this decision, for all the club members and for football in general, '' the president said on the club website.
"We have always made it clear that we consider FIFA's sanction to be disproportionate. This judgement by CAS, which ratifies FIFA's decision, is not good for us and defies all sporting logic.''
Barca were found guilty of breaching FIFA's rules on the transfer of players aged under 18. The players in question were registered and participated in competitions with the Catalan club between 2009 and 2013.
Bartomeu said strict compliance to a poorly drawn-up rule had been prioritised above the spirit in which the rule had been written, and vowed to lead a campaign to change FIFA regulations.
"FIFA and its president (Sepp Blatter) have to be an organisation which protects the footballing world, and decisions like this distance it from this objective,'' he said. "We do not feel supported or protected by those people who should be doing this.
"The strict letter of the law has been observed, rather than the spirit in which it was written and a precedent that is not good for the game in general has been created - one which has attempted to tarnish the good name of our club. I wish to announce that Barca, with myself in the lead, will fight to change this regulation and improve it.
"I hope that FIFA will show sufficient common sense to rewrite this regulation and that no other club will have to suffer this injustice.''
The Catalan club went on a summer spending spree this year while the suspension went on hold during the appeals process, splashing out more than 150 million euros on Luis Suarez, Ivan Rakitic, Marc-Andre ter Stegen, Thomas Vermaelen, Claudio Bravo, Jeremy Mathieu and Alen Halilovic -- something Bartomeu acknowledge was done with the long term very much in mind.
"I remain optimistic,'' he continued. "On the one hand, we have a squad which offers sufficient guarantees to cover any possible needs of the first team and, on the other, we have to bear in mind that the signings we made last summer to strengthen the squad were made with the possibility of this sanction in mind and to allow us to contend for all the possible titles we are competing for until this sanction is over.''