Giuseppe Conte, 54, says on his resume that he "perfected his legal studies" at New York University.
But a spokeswoman for the institution told the New York Times that there is no record of him having studied there.
The Five Star Movement and its prospective coalition partner, the League, are awaiting approval from Italy's president to form a government.
"A person by this name does not show up in any of our records as either a student or faculty member," a spokeswoman told the New York Times newspaper.
She added that Mr Conte may have attended "one or two-day programmes" for which there are no attendance records.
His CV is publicly available on the Chamber of Deputies website and is dated 17 September 2013.
It says that he "perfected and updated" his studies at New York University for at least a month every summer between 2008 and 2012.
One of the parties that proposed Mr Conte as prime minister has disputed the allegation that his CV contains inconsistencies.
"[He] had written at no point to have completed courses or masters at the university," the Five Star Movement said in a statement, adding that he had gone there to perfect his English language skills.
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