Santos have accused Barcelona of using a "smokescreen" to avoid paying an supposed EUR2million clause in Neymar's contract after the player was named on the Ballon d'Or shortlist.
The Brazil international joined the Spanish champions in 2013 but some details of the move have proven a source of contention, with Santos having filed a complaint with FIFA over the transfer.
Santos claim they are due an extra EUR2m as Neymar was named on the shortlist for the Ballon d'Or this year.
However, Barca are alleged to have leaked a letter to the media this month suggesting they will not pay the bonus while the overall terms of the initial deal remain under investigation.
And this week Santos released a statement accusing Barca of using a smokescreen to avoid the payment.
"Santos Futebol Clube (SFC) wishes to respond publicly to fans' questions raised following the recent publication of a purported letter of FC Barcelona ("FCB") dated December 14, 2015," the Brazilian club said.
"The original letter was never received by SFC and SFC could not disagree more with its contents.
"SFC demands the respect of the confidentiality that rules FIFA's arbitration procedure and urges the involved parties to abstain themselves from violating that obligation of confidentiality.
"On the other hand, in another clear example of legal unfulfilment, it seems that FC Barcelona (FCB) says in its letter that it won't carry out the payment owed to SFC, following Neymar Jr's nomination as a FIFA World Player finalist.
"The formal impediments supposedly aforementioned by FCB in order to make the payment do not exist in reality. Consequently, FCB is merely using smokescreens to avoid their legal obligations."
Santos closed their statement by warning that they will "adopt as many measures as necessary" to claim money they feel owed to them, once an official response is received from the Catalan club.