Senior Samajwadi Party leader and Rajya Sabha member Mohan Singh passed away at the All India Institute of Medical Sciences in New Delhi on Sunday after a prolonged battle with cancer.
Singh, 68, was admitted to AIIMS on September 18, party spokesman said.
AIIMS medical superintendent PK Sharma said, "Singh was admitted a week ago, and was suffering from one type of blood cancer."
"Two days back his condition became serious and he was shifted to ICU. He died at 4:15 pm on Sunday."
SP supremo Mulayam Singh Yadav, UP Chief Minister Akhilesh Yadav, UP Assembly Speaker Mata Prasad Pandey and several party leaders have condoled his death, party spokesman Rajendra Chowdhury said in Lucknow.
His body will be brought to Lucknow on Monday and put in party office at Vikramaditya Marg, Chowdhury said.
Singh's last rites will be performed at his home district Deoria.
Singh, a veteran socialist leader and a friend of Madhu Limye, was a three-time Lok Sabha MP from Deoria. He also served as minister in UP cabinet.