He replaces Senate leader, Ali Ndume.
At the resumption of plenary on Tuesday, Senate President Bukola Saraki read a letter written to the Senate by the All Progressives Congress caucus, informing the lawmakers of its decision to name Senator Lawan as the new Senate Leader.
But in a swift reaction, Senator Ndume told journalists that his removal as Senate leader came as a surprise as he was not aware that he had been removed and replaced.
The reason for the removal of Senator Ndume was not made known, but recently the senator had told reporters that the non-confirmation of Ibrahim Magu as EFCC Chairman did not amount to a rejection.
The Senate Spokesman, Sabi Abdullahi, later restated the Senate’s position, insisting the lawmakers rejected Mr Magu, as opposed to Senator Ndume’s statement.
It is the first day of legislative proceedings for the year.
Lawmakers welcomed each other back to work after the Christmas and New Year holiday.
They settled down for the business of the day and the Senate President reeled out the areas that the upper chamber would give priority-one of which is the consideration of the 2017 budget.
As legislative proceedings for the day wound down, Senator Saraki announced a change in the leadership of the Senate.