The Crime Branch of Delhi Police detained Farhat, Personal Assistant to Rajya Sabha member Munavvar Saleem, from Uttar Pradesh on Friday night.
According to police sources, Farhat used to hand over official documents to Akhtar for money. He had come into contact with the Pakistan High Commission some years ago.
On Saturday, the MP sacked Akhtar and said he regretted employing him.
Three Indians from Rajasthan have been arrested in connection with the spy ring. They are Maulana Ramzan and Subhash Jangir, who were trapped along with the Pakistani official here, and Shoaib.