An unnamed former senior Justice Department official told New Yorker reporter Jane Mayer that Lynch asked Comey to follow Justice Department policy of not commenting on investigations or taking steps which could have an effect on the outcome of an election.
The FBI director refused, according to the official, and said that he had promised to inform members of Congress of any further developments regarding the probe.
Comey also argued that the proximity of the presidential election was a reason to inform the public despite Justice Department policy and tradition, according to the New Yorker report.
In a March 2012 memo to department employees, then-Attorney General Eric Holder urged to be "particularly sensitive" in the treatment of investigations taking place "near the time of a primary or general election" which could affect results.
"Politics must play no role in the decisions of federal investigators or prosecutors regarding any investigations or criminal charges," Holder wrote.
The former senior Justice Department official told the New Yorker that Comey's decision was "aberrational" and "violates decades of practice."
"It impugns the integrity and reputation of the candidate, even though there’s no finding by a court, or in this instance even an indictment," the official said.