After the party fell short of the legal limit, he allegedly broke the Electoral Act.
The Prime Minister says she's awaiting the outcome of the investigation.
She's accusing him of dirty politics and saying he should be sacked.
Ricardo Menendez March will stand in Auckland's Maungakiekie electorate.
Does Parliament still want this current Government in charge?
"I want to end this charade we've been in."
But the Deputy Prime Minister will likely stay in his role for the moment, writes Duncan Garner.
"It will dog this Government throughout this year."
Support for Winston Peters' party slipped to 3.6 percent.