Sepp Blatter has written to FIFA's 209 member associations protesting his innocence and criticising FIFA's ethics committee for being "tendentious and dangerous" ahead of disciplinary hearings later this week.
The 79-year-old outgoing FIFA president also claims the proceedings against him have been "like an inquisition". Blatter and UEFA president Michel Platini will have hearings before FIFA ethics judge Hans-Joachim Eckert on Thursday and Friday in Zurich over a ?1.3million payment made to Platini by FIFA in 2011.
Blatter, who is currently provisionally suspended, has written to the associations saying: "I am bewildered by the insinuations and allegations brought against me by the investigatory chamber of ethics committee.
"However the way in which the investigatory chamber of the ethics committee has communicated on the current proceedings, demanded the maximum penalty and reinforced public prejudgement has reached a tendentious and dangerous dimension.
"These proceedings remind me of the Inquisition.
"I will continue to fight for my rights and at the end of this week I will present my case before the adjudicatory chamber with great conviction and a strong belief in justice."
Blatter and Platini are likely to escape lifetime bans for corruption but investigators expect the pair to receive lengthy suspensions of at least seven years.
They face charges including corruption, conflict of interest and non-cooperation. Sources with knowledge of the case say that it will be difficult to prove corruption, which carries a lifetime ban, but believe there is clear evidence of a conflict of interest in the payment being made.
Blatter's case will be heard on Thursday with Platini's following on Friday, with a decision expected on Monday next week.
The 2million Swiss franc payment was made to Platini in February 2011. The Frenchman and Blatter say the payment was honouring an agreement made in 1998 for work carried out between 1998 and 2002 when Platini worked as a technical advisor for the FIFA president.
However the payment was not part of Platini's written contract - they have insisted that it was a verbal agreement which is legal under Swiss law.
The timing of the payment has raised eyebrows however. It took place nine years after Platini had stopped working for FIFA, and was made while Blatter was seeking support for a fourth term as president. Several weeks after the payment was made Platini and UEFA's executive committee endorsed his candidacy.
Blatter says in his letter that one of the values passed on to him by his parents was to always pay off his debts.
He adds of the Platini payment: "I can assure you that it was legal because it was based on a verbal agreement. And agreements must be adhered to.
"This payment was put through the full administrative process, the correctness of which was confirmed by all competent FIFA bodies including the Congress."
Blatter's personal advisor Klaus Stoehlker said Blatter had been working on the letter on Monday and had sent it to the 209 associations because he wanted to tell them in person of his feelings about the charges.
"He has worked very hard on this letter, he is looking at this week feeling very strong in spirit," he told Press Association Sport.
Platini has also denied any wrongdoing - he has said he had not been paid the full amount agreed in 1998 because of FIFA's financial situation at the time.