The PN has slammed the "biased" behaviour of Speaker Anġlu Farrugia after he threatened to kick an MP out of parliament on Monday.
Karol Aquilina was left fuming after Farrugia blocked his request to amend a motion calling for a public inquiry into the construction site death of worker Jean Paul Sofia.
Aquilina described the decision as "obscene", provoking the ire of the Speaker, who threatened to throw him out of the chamber. However, he instead suspended the sitting.
In a Facebook post on Tuesday, Aquilina accused the Speaker of being "complicit" with Prime Minister Robert Abela to prevent a public inquiry into the construction worker's death in December.
The Nationalist Party said it condemned "the incorrect and biased behavior" of the Speaker.
"The Speaker denied the Members of Parliament of the Nationalist Party of their right to submit a motion to make an amendment to the amendment proposed by the government," it said, citing parliamentary 'bible' Erskine May.
Parliament will vote on Wednesday on whether to support a motion calling for a public inquiry into the death of the 20-year-old.
A petition set up by his mother Isabelle Sofia Bonnici, which called for the inquiry, beat its target of 15,000 signatures by Tuesday afternoon.
The prime minister has repeatedly resisted calls for a public inquiry, insisting that a magisterial inquiry is enough.
The PL has amended the motion for the inquiry to remove all reference to a public inquiry and instead implore the inquiring magistrate to speed up her inquiry.