The Nigerian leader faced relentless pressure from civic groups before giving assent to the crucial amendment on Friday.
Mr Buhari assented assented to the bill at the Council Chamber of the Aso Villa, Abuja on Friday afternoon.
“Are you fair to the 160 million Nigerians using their wealth just to conduct (a) primary election to produce a party candidate, despite other demands by the public?”
The speaker said collection of signatures against the president was not an easy task as is being speculated.
Activists and Civil Society Organisations enjoined the National Assembly to enforce their veto to ensure the passage of the Electoral Amendment Bill rejected by Mr Buhari.
Their actions in hampering the credibility of future Nigerian elections could have a telling impact on the advancement of democracy.
“We must do this work before we go on recess and we must do it thoroughly,” the speaker said.
Irregularities that dogged previous elections would be corrected in the proposed reforms.
