Akhilesh Yadav has appointed Pandey, SP MLA from Itwa in Siddharth Nagar district, the leader of opposition in the assembly, a party leader said.
At a meeting held earlier at the SP headquarters here, the party MLAs had authorised Akhilesh Yadav to choose the LoP.
The SP also appointed Kamaal Akhtar as the chief whip and Rakesh Kumar alias R K Verma as the deputy whip in the assembly, a party release said.
Pandey, a Brahmin, has held the post of Uttar Pradesh Assembly speaker twice -- 2004-2007 and 2012-2017.
He was first elected as MLA in 1980 and then in 1985 and 1989. He served as state health minister between 1990 and 1991 in the then chief minister Mulayam Singh Yadav's government.
He was the labour and employment minister in Mulayam Yadav's government between 2002 and 2004.