Venkat Prasad, who runs an advertising agency, was arrested from Abids area of the city, a police official said. According to the official, Venkat had met Prahlad Modi when he had visited the city earlier.
"After that (visiting Modi), he started claiming himself as secretary to Prahlad Modi and made calls to few senior bureaucrats in Delhi seeking favours, and also fixed appointments with some other officers," he said.
Venkat's cover was blown after an official raised suspicion and alerted the police.
The police official said that Venkat had put his name as the "secretary PMO Modi" on the Truecaller app and whenever he used to make calls to officials his name would get displayed as "Secretary PMO Modi".
A case of cheating and extortion under relevant sections of IPC was registered against the accused. Further probe is on.