Bahujan Samaj Party leader Ram Prasad Chaudhary from Basti joined the Samajwadi Party along with his supporters on Monday.
Along with Chaudhary, 200 leaders, including three former MLAs and six district panchayat members also took membership of the SP.
On November 23, BSP chief Mayawati had expelled Chaudhary from the party for indiscipline, after which there was speculations that he could join the SP.
Chaudhary reached the SP state office with a convoy of around 2,000 vehicles from Basti and also deposited the toll tax at the toll plaza.
A former cabinet minister of UP, Chaudhary was a known face of the BSP in Basti division and was elected to the Assembly five times from Kaptanganj in Basti.
In the last Lok Sabha election, he was fielded by the BSP but lost to the Bharatiya Janata Party candidate.
Apart from Chaudhary, those who joined the SP included former MP Arvind Chaudhary, former MLA Dudhram, Rajendra Chaudhary and Nandu Chaudhary.
Once a confidant of BSP chief Mayawati, CL Verma and former minister Raghunath Prasad Shankhwar also joined the SP. Former Hindu Yuva Vahini chief and once trusted lieutenant of Chief Minister Yogi Adityanath, Sunil Singh, had joined the SP along with his supporters on Saturday.