President Muhammadu Buhari and former Vice-President Atiku Abubakar were the leading contenders in the election.
The Independent National Electoral Commission (INEC) had declared APC winner of the election.
Although Atiku and his party challenged the outcome of the election from the tribunal up to the Supreme Court, they could not upturn the victory of Buhari.
Speaking when he featured on Politics Today, a Channels Television programme, on Thursday, Mohammed alleged that fraud on the part of either INEC or security operatives cost his party the election.
He said Nigerians knew what transpired during the 2019 elections, adding that his party has learnt its lessons.
“The general impression within the party and within the country is that we actually won the election and that we lost to a lot of fraud, to a lot of manipulations that was perpetrated by either the electoral umpire or by the security operatives.”
“We are not only looking at the other side and playing the blame game that is the fault of this present administration. We are also critical with ourselves, where we have some gaps, loopholes and inadequacies.
“We are not only looking at the other side, but we are also looking at ourselves, looking at our internal politics, and giving a level playing field for the youths and women who are a majority in terms of demographics and in terms of interest.
“And of course, making sure that the electoral umpire, the INEC that is now instituting some reforms will also become impartial.”