66-year-old Singh, a 1974 batch IAS officer, died at a hospital here.
He was appointed advisor to the CM on July 26.
"Singh suffered heart attack and was rushed to Civil hospital where he breathed his last," an official spokesman said.
The Chief Minister and Governor Ram Naik have condoled the death of Singh.
Samajwadi Party chief Mulayam Singh Yadav and the CM had visited him in the hospital.
Singh had served in the Ministry of Defence when Mulayam Singh Yadav was Defence Minister and then again as his Secretary when he was Chief Minister of UP.