The Daily Post reporeds that two Sanma Province MPs, Hosea Nevu and Marc Ati, have both left the People's Progress Party.
The leader of the Vanua'aku Pati, Joe Natuman, welcomed the pair into the country's oldest political party at a kava ceremony in Port Vila.
It meant the party now has eight MPs, making it the biggest party in the coalition government led by Charlot Salwai.
Mr Natuman, who is the Deputy Prime Minister, said the move by the two MPs would help mitigate efforts to undermine Vanuatu's interests on West Papua.
