The PNC MPs moved after Prime Minister James Marape asked them to move out of the Government side.
Party leader and former Prime Minister, Peter O’Neill, led his group.
A total of 14 PNC MPs are now in the Opposition, and the Speaker makes 15.
In a statement on June 2nd, O’Neill said PNC has now moved to the Opposition “so that we can confront this failing Marape leadership”.
“It is our duty to bring to light the terrible and depressed state of the government under his authority,” O’Neill said.
On the other hand, Prime Minister Marape said: “My Government is cleaning up on a lot of mess, the last one year, due to O’Neill led government of recklessness, camouflaging with shady infrastructural contracts and feel-good public policies like free education that gave them licence to recklessness.
“That mess, we the present Government, have inherited and are responsibly cleaning, including settling their debts and liabilities.
“The PNC leader continues to play politics, so unfortunately his Members in my Government benches will have to move tomorrow to the Opposition benches.”