Parliament resumed just long enough for the deputy speaker Francis Marus to drop a bombshell.
In a short statement, he said last week's Supreme Court ruling meant Sir Michael Somare is PNG's legitimate prime minister.
He then declared the PM's office vacant because Sir Michael had missed three consecutive sittings of parliament since January.
Mr Marus said electing a new Prime Minister will be the first item on Wednesday's agenda for parliament, and then he adjourned the sitting.
PNG's effective Prime Minister Peter O'Neill wasn't in parliament.
His deputy Belden Namah was and he looked stunned by the announcement and said a caucus meeting would be held to get legal advice.
The latest move comes just hours after a senior judge has appeared in court charged with sedition, the second in less than a week, over the Supreme Court's ruling.
Justice Nicholas Kirriwom made a brief appearance in just a committal court a short walk from his chambers in the Supreme Court.
Magistrate Jimmy Tapat read out the charge of sedition and said it's alleged Justice Kirriwom conspired with the Chief Justice, Sir Salamo Injia, to take sides against the state.
Justice Kirowom made no comment and the matter was adjourned to July.
The Chief Justice was charged with the same offence in dramatic fashion after police and soldiers tried to arrest him in his courtroom last week.
The government of Peter O'Neill made the complaint against the two judges after the Supreme Court ruled last week for the second time that Mr O'Neill is not PNG's legitimate prime minister.
Elections in Papua New Guinea are scheduled for June 23, and the parliament had already been dissolved in preparation for them.