Farhat, the PA of SP's Rajya Sabha MP Munabbar Saleem, was detained last night, said a senior Crime Branch officer, adding his interrogation is underway.
Delhi Police is also trying to nab other members of the racket who, it believes, were in close contact with Pakistan High Commission staffer Mehmood Akhtar who was caught receiving secret documents here on October 26.
Two others, Maulana Ramzan and Subhash Jangir, residents of Nagaur, Rajasthan, were held along with Akhtar. Another accused Sohaib was detained in Jodhpur and brought to Delhi by the police where he was arrested.