"Mr Mandal this evening handed over the resignation to me at my residence", said assembly Speaker Govind Singh Kunjwal.
In his resignation letter, Mandal said he was resigning "in the larger interest of his constituency".
Kunjawal said he has accepted the resignation with immediate effect on the request of Mandal.
PCC chief Yashpal Arya and other senior Congress leaders were present at the residence of Kunjwal when Mandal handed over the resignation.
Mandal told the Speaker that there were lot of problems related to Sitarganj constituency like land ownership rights to Bengalis and opening of new schools and colleges.
All these issues are expected to be addressed by the new Congress government, Mandal said.
Mandal also said he has urged Bahuguna to contest from Sitarganj seat.