The Papua New Guinea parliament is to try again to elect a new governor-general after the Supreme Court ruled that Sir Pato Kakaraya was not chosen in a lawful manner.
The chief justice, Sir Mari Kapi, has ruled that it was contrary to the law for the speaker to cast the deciding vote.
He also ruled that the clerk of parliament failed to disallow defective nomination forms in the election last December.
The case had been brought by the losing candidate, Sir Albert Kipalan, who himself was chosen as governor general in an election in September which the Supreme Court declared invalid because of a faulty nomination process.
Parliament was adjourned in January for five months and the prime minister has said he will only recall the house earlier to swear in a new governor general.
In response to the ruling, Sir Michael Somare, said he would call a special cabinet meeting tomorrow to discuss the court ruling.
The term of the last governor general, Sir Silas Atopare, ended in November.