The post became vacant following the defection of its former occupant, Senator Emmanuel Bwacha (Taraba South) to the All Progressives Congress (APC) at the weekend.
President Muhammadu Buhari officially received Bwacha into the APC at the State House last Thursday.
Senate President Ahmad Lawan read a letter from the National Chairman of the PDP, Dr Iyorchia Ayu, announcing the choice of Senator Lau as the new Deputy Minority Leader of the upper chamber.
Bwacha was officially recognised as a member of the APC on Tuesday morningon the floor by Lawan.
Kalu promptly carried out the instruction even as members of the minority PDP kicked against the development.
Lawan said with the crossing over of Bwacha to the APC, the party now has 70 members in the Chamber while PDP has 38 leaving Young Progressives Congress (YPP) with one .
Senator George Sekibo efforts at drawing the attention of the Senate to the abnormality and illegality of Bwacha’s defection met with a brick wall.
The Senate President ruled him out of order citing the letter by the National Chairman of the PDP, Ayu, appointing a replacement for Bwacha.
