Papua New Guinea's Registrar of Political Parties and Candidates says MPs-elect should stay with the party under whose banner they were voted into parliament.
Dr Alphonse Gelu's comment was made as some MPs-elect appear to be moving towards the People's National Congress party of re-elected prime minister Peter O'Neill.
The new MP for Moresby Northeast, John Kaupa, was a member of the PNG National Party and defeated a PNC candidate to win his seat.
After winning he immediately joined Mr O'Neill's group, against the wishes of his own party.
Dr Gelu said that since the Organic Law on Political Parties and Candidates was changed in 2010, MPs could switch parties at will.
"Because that provision was removed by the Supreme Court in 2010, now there is really nothing there to stop them from doing that.
"But now this is what we have been saying that we have been asking our leaders not to that. Once you are sucessful with a party, you must stick with that party but you know John Kaupa has proven otherwise."