The losing Cook Islands Party candidate in last week's by-election, Teariki Matenga, has filed a petition, challenging the eligibility of 20 voters.
Mr Teariki lost against his sister and political rival of the Democratic Party, Selina Napa, who won 14 more votes to secure the Titikaveka seat.
The opposition leader, Wilkie Rasmussen, says Ms Napa's team is still formulating a response.
He says the party is sensitive to the fact it was contest between a brother and a sister but now this latest puts the party in two minds about whether the Cook Islands Party really stands for its motto of the party of love.
The by-election followed the death of the opposition leader Robert Wigmore.