Sir Michael Somare was reinstated as prime minister by Supreme Court tonight.
Three judges voted for and two declined to vote.
The two judges said they did not vote because the judiciary had been compromised.
O'Neill held a press conference tonight.
"Judges Gibbs Salika and Bernard Sakora accused Chief Justice Salamo Injia and Nicholas Kirriwom of lacking integrity and disqualified themselves from today's referral decision to determine legitimacy of O'Neil-Namah governmentt," reports Susuve Laumaea.
"Government has called emergency Parliament session tomorrow to deal with what is now widely seen as tainted and corrupt."
A majority opinion of three Supreme Court judges - Chief Justice Sir Salamo Injia, and Justices Sao Gabi and Nicholas Kirriwom – was that the election of O’Neill as Prime Minister was illegal.
Deputy Chief Justice Gibbs Salika and Justice Bernard Sakora declined to publish their opinions.
The majority ruling was that: “The re-election of Peter O’Neill was made in breach of the binding opinion and declarations and orders made by this court on 12 December 2012.
“Parliament should have exercised patience and await the judgment of the court, and complied with the binding opinion and declarations and orders by allowing Sir Michael to resume his seat in parliament before a motion, if any, is entertained by the speaker to remove him as prime minister in accordance with the constitution.”
The court also interpreted that the Prime Minister and National Executive Council (Amendment) Act passed to set a minimum age limit at 72 being unconstitutional as it stopped a person’s “right to stand for elective public office".