Sherwani, a five-term MP from Badaun, was welcomed into the party by SP President Akhilesh Yadav.
Akhilesh told reporters "The Samajwadi Party will make a comeback in the 2022 Assembly elections and also determine the course of the national politics."
He lashed out at the Yogi Adityanath government and said that it had "failed" to control coronavirus pandemic as well as crime in the state.
He alleged that the government was making false claims about investments in the state and that investment summit had falied to yield any results.