Maori Party MP for Waiariki Te Ururoa Flavell is challenging for the leadership of the party.
Maori Party co-leader Pita Sharples confirmed Mr Flavell's challenge for his position at Ratana Pa near Wanganui during the annual Ratana celebrations.
Maori Party co-leader Tariana Turia had always planned to step down from party leadership before next year's general election and her replacement was likely to be announced at Ratana this week.
Dr Sharples reportedly said in his arrival speech that he would stand down if asked to by the party.
A meeting to discuss the leadership issue, led by Maori Party president Pem Bird, is underway at Ratana.
Mr Bird told The Daily Post a number of issues would be discussed at the meeting, including the party's leadership challenge and discussion on a replacement for Mrs Turia.
Mr Bird said the meeting would last at least five hours.
"But the party must first consider a request for a special meeting to discuss the leadership issue as per our constitution."
Mr Bird said he did not expect a final decision on the leadership issue to be made today.