Former Prime Minister Ranil Wickremesinghe said he would form a "new UNP" with a new group of leaders.
Speaking to the media at the party headquarters 'Sirikotha', Wickremesinghe said the party had drastically lost the Sinhala-Buddhist voter base.
"We have never experienced such a setback before. We must investigate the reasons behind this setback," he added.
Wickremesinghe said responsibilities were shared equally among all organizers in the party.
"I was entrusted with the task of securing votes from the North and East provinces - which I fulfilled to the best of my ability. Others too were given similar responsibilities," he added.
The former Prime Minister said no party official responsible for Premadasa's campaign funds during the election.