The Papua News Guinea agriculture and livestock minister Tommy Tomscoll has resigned as member of the People's Democratic Movement Party.
Mr Tomscoll will be the first minister to resign from a party in the government coalition to join another coalition partner.
Sources close to the minister say he is likely to join the prime minister's People's National Congress Party.
The minister and member for Middle Ramu told the party secretary in a letter that he had given the matter long and careful consideration.
He was first elected to parliament under the People's Democratic Movement banner in 1997.