Criminal behaviour by Czech man Karel Sroubek forced a New Zealand family into witness protection, Simon Bridges claims.
The National leader made the statement in Parliament on Tuesday.
"Is a criminal, with charges so serious that an entire family went into a witness protection scheme, someone who should have residency in New Zealand?" he asked the Prime Minister.
Jacinda Ardern said the Government would share more information around the case "when we are in a position to [do so]".
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Court documents obtained by NZME allegedly show Sroubek faced criminal charges for assisting in an assault of a man over an unpaid debt.
He was granted permanent residency while in prison, sparking widespread outrage as many people were left concerned the Government didn't do a full investigation into Sroubek's nature.
Mr Bridges asked Prime Minister Jacinda Ardern on Tuesday in Parliament whether she was aware of Sroubek's alleged involvement in the assault of one of his associates.
The court documents reveal that Sroubek, then going by the pseudonym 'Jan Antolik', went to his associate's home with two other men, NZME report. It's then claimed he assaulted the associate and threatened him with a knife over a $12,000 debt.
Sroubek and the two others involved in the assault had Hells Angels connections.
NZME report that the three men took the alleged victim's watch and his partner's car, but said the debt was still owed.
The associate reportedly sought to give evidence against Sroubek, but his application was denied.