Sepp Blatter has been called a "hypocrite and a liar" by FIFA presidential contender Chung Mong-joon.
It is the latest outburst in an ongoing spat between the pair. Dr Chung, who announced in August he would be standing as a candidate to replace Blatter in February's elections, also stated he was planning to sue the outgoing president.
Blatter has come under close scrutiny for not stepping down with FIFA's main sponsors demanding last week he should resign after Swiss authorities said they had opened criminal proceedings against him.
The 79-year-old has denied any wrongdoing and said through his US-based lawyer that "leaving office now would not be in the best interest of FIFA nor would it advance the process of reform".
Dr Chung, a former FIFA vice-president and a member of the FIFA executive committee until 2011, claims "FIFA has become a corrupt organisation serving the interests of a few."
The South Korean is facing a suspension by the FIFA ethics committee for promoting a $US777m (£508m) development fund proposed by his nation's 2022 World Cup bid. He said that was a "travesty of justice" after no investigation was lodged against UEFA president Michel Platini's support for Qatar.
Dr Chung calls it an attempt by FIFA to undermine his candidacy to replace Blatter in the February 26 election.
He added he was preparing to sue Blatter in court for "embezzlement" for being paid a secret salary which was
not even agreed by FIFA's executive committee.
Dr Chung added: "FIFA has become a badge of shame. To call it a mafia is almost insulting to mafia, so blatant and arrogant is its corruption.
"At FIFA money and power have blinded Blatter in the virtues of sportsmanship. For his payment without executive committee approval, I plan to sue Mr Blatter for embezzlement in court. Mr Blatter in short is a hypocrite and a liar."
Chung pointed out that Chilean Harold Mayne-Nicholls was banned for seven years by FIFA's ethics committee after asking Qatar for placements for family members while he was in charge of the technical inspectors looking at the World Cup bids. Mayne-Nicholls last year said he wanted to run against Blatter for the presidency.
He added: "Mr Platini voted for Qatar and his son landed a job with a Qatar company as chief executive. The ethics committee did not even start an investigation, this is a travesty of justice."