Argent joined earlier this month, following Johnson's former media strategist Guto Harri's move to the media company.
Argent reports to Harri, who was hired to restore the media company’s reputation after the phone-hacking scandal and ongoing Leveson Inquiry.
She sits in the corporate affairs team and is responsible for long-term planning and projects.
Before running the London Mayor’s operations, Argent was head of events for the ‘Back Boris’ campaign. She was also an events manager for the Conservative Party in 2006-07.
Argent will not be responsible for media relations, which will continue to be handled by News International’s head of external comms Daisy Dunlop.
The appointment comes after BAA’s senior media relations manager Mary Kearney joined News International as corporate comms manager at the beginning of March.
News Corporation, owner of News International, has recently announced it is considering plans to split the business in two.