Papua New Guinea's Registrar of Political Parties and candidates says for MPs to switch to a new party from the one which endorsed them as a candidate in the election is a breach of organic law until after government is formed.
Dr Alphonse Gelu's comment follows a move by a regional candidate in West Sepik Province to shift alliance from the Triumph Heritage Empowerment party to the PNG Party.
Although leading the count to become the new West Sepik Governor, Amkat Mai has announced his decision to move, even before the conclusion of counting and elimination.
Dr Gelu says he will issue a ruling on Mr Mai's intended switch this week because such moves undermine the system.
"We will still maintain him under the THE Party because he was officially endorsed by that party and that is part of the process according to the Organic Law on national elections. The law is still very much in operation here so that person cannot switch now."
Dr Alphonse Gelu says that Mr Mai is free to join the PNG Party after the formation of a government.