Mark Pieth, a Swiss criminal law professor who has led reform drives at FIFA, made the comments after the head of the world body's independent audit committee, Domenico Scala, quit in protest at what he called an attack on FIFA's reforms.
Infantino "has dropped the mask," of a reformer, Pieth told AFP. "He is showing his real motives and his real personality."
Pieth further accused Infantino of not respecting the need for checks on power.
Pieth, who is close to Scala, also indicated that the FIFA boss pushed Scala to resign following a dispute over Infantino's proposed salary.
Scala sat on the remuneration committee tasked with recommending Infantino's pay which is still to be decided.
Scala stepped down yesterday, voicing concern over a measure that gave the FIFA Council control of the nomination of members of independent oversight bodies such as its ethics committee and audit and compliance committee.
The measure was approved at this week's congress in Mexico City, the first since Infantino replaced Blatter as president.
But Pieth argued that giving executives the power to
appoint and dismiss investigators was troubling and recalled the Blatter years, when the scandal-tainted leader controlled who probes would target.
Infantino "is trying to establish total control," Pieth claimed.
- Money dispute -
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Infantino told journalists on Friday that his compensation had not yet been decided.
According to Pieth, who did not disclose his source for the information, Infantino is upset that FIFA's remuneration committee determined his annual salary at 2 million Swiss francs ($2 million, 1.8 million euros) without the prospect of a bonus.
"FIFA is dismayed to learn that Prof. Pieth would have any information pertaining to compensation matters relating to FIFA personnel, as these matters are private and confidential," a FIFA spokesperson said in a statement.
"FIFA is concerned that certain individuals may be seeking to advance their own agenda to the detriment of football, making claims that are baseless and without merit."
Under reforms passed by FIFA in February the salaries of top officials are to be released. Blatter always kept his wage a secret, but FIFA revealed in its annual report that he received 3.63 million Swiss francs ($3.7 million/3.3 million euros).
A fresh crisis that erupted a year ago after US prosecutors charged dozens of senior football officials with corruption brought Blatter down and led to Infantino's election as president in February.
