A Rashtrapati Bhavan communique said that Mukherjee would hold additional charge from Saturday until the recovery of the Prime Minister.
"The President of India, as advised by the Prime Minister, has directed that Pranab Mukherjee, Minister of External Affairs is assigned the additional charge of Ministry of Finance from January 24, 2009 until the recovery of the Prime Minister from medical treatment," the communique said.
Singh was holding the finance portfolio since last month when P Chidambaram was moved to Home Ministry in the wake of the Mumbai terror strike.
However, Chidambaram is assisting Singh in answering questions related to Finance Ministry in Parliament.
With the development, Mukherjee is expected to present the interim budget in the Lok Sabha on February 16.