Former Bihar police chief Gupteshwar Pandey, who took voluntary retirement from service a few days ago, joined the state's ruling JD(U) on Sunday.
Pandey, an outspoken police officer, joined the party in the presence of Chief Minister Nitish Kumar, who is also the JD(U) president.
The 1987 batch IPS officer had strongly defended Kumar on the issue of institution of a CBI probe into the mysterious death of actor Sushant Singh Rajput.
Ever since he took VRS weeks before the October- November assembly elections, there was speculation that he could take the political plunge.
"Nitish Kumar ji personally called me