La Liga president Javier Tebas has rejected Barcelona's explanation for the payments that were made to a former vice-president of Spain's referees' committee.
The Catalan giants are currently under investigation for paying €7.3m (£6.4m) between 2001 and 2018 to two companies which were owned by Jose Maria Enriquez Negreira.
UEFA are conducting their own investigation, which could lead to Barcelona being banned from the 2023-24 Champions League.
The La Liga club have been accused of fraudulent management, breach of trust and falsification of business documents, with the investigation into the payments beginning in May 2022.
Barcelona president Joan Laporta remains convinced that his club will be able to clear their name.
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The Catalan outfit continue to insist that they simply paid for technical reports on referees, but this explanation has been rejected by Tebas, who spoke at a press conference on Wednesday afternoon.
"He said the same thing as in the press conference. It was the same, that the payments were for arbitration advice. Personally, I have already told him that I don't think he was convincing with his explanations. I have been saying that for several days," Tebas said.
"It is incomprehensible that Barca was paying the vice-president of the referees for so many years. We have asked the investigating court to include Negreira's son as a person under investigation.
"I don't think Barcelona bought referees, but there are indications that the payments were intended to influence. The mere intention can be punishable conduct.
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"With Barca, there has always been communication, maybe not with Laporta. He said I hadn't called him. He was the one who should have called.
"It was FC Barcelona who committed the irregularity. We always have conversations with all clubs. We have spoken for two minutes."
Former Barcelona presidents Josep Maria Bartomeu and Sandro Rosell have also been hit with charges of corruption as part of the investigation.
"Consulting on technical-refereeing issues does not constitute any kind of illegal act. Consulting - as is done by the big clubs - was carried out transparently, with the corresponding invoices, at least in my first mandate as president," read part of Laporta's recent statement on the situation.
Barcelona will return to La Liga action at home to Atletico Madrid on Sunday afternoon, with the Catalan outfit looking for their first win since the start of the month.
