Chidambaram has been lodged in the Tihar Jail under judicial custody since September 5.
The two Congress leaders were accompanied by Karti Chidambaram, the former Finance minister's son who is also a Lok Sabha MP.
The former Union Minister was sent to judicial custody by a Delhi court after his arrest on August 21 by the Central Bureau of Investigation (CBI) for alleged irregularities in granting Foreign Investment Promotion Board (FIPB) clearance of Rs 305 crore to INX media, now known as 9x news, during his tenure as the Finance Minister.
Chidambaram is also being probed by the Enforcement Directorate (ED) in money laundering case relating to INX media.
The Congress had accused the BJP-led central government of indulging in political vendetta.
A bail application has been filed by the lawyers of P Chidambaram before the Delhi High Court.
This is for the first time that Sonia Gandhi and Manmohan Singh have visited the jail premises to meet any party leader lodged there.
Chidambaram has been lodged in Jail No. 7 of the Tihar jail, which is meant for economic offenders.
After meeting his father, Karti Chidambaram said: "My father and my family are extremely grateful to Congress President Sonia Gandhi and former PM Dr Manmohan Singh for visiting him today and for extending their support. It's a big boost for us in this political fight."
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