The former Governor had maintained a low profile since his exit from City Hall.
Kidero filed an application at the High Court seeking to be enjoined in a case challenging Sonko’s election as Nairobi Governor.
Kidero’s move is the latest after changing his position on several occasions with regard to the August 8 election.
Immediately after the August 8 election, Kidero had vowed to challenge Sonko’s election on grounds that the results were manipulated by a computer algorithm.
However, the former Governor announced he had conceded defeat while attending Sonko’s swearing-in ceremony. He had also announced that he would support the new administration led by his rival in the August 8 general election.
“I promised a smooth transition and I have no problem referring to Mike Sonko as my Governor. I am always available for consultation,” Kidero remarked.