Labour MPs Trevor Mallard and Andrew Little have not responded to a 5pm deadline set by Judith Collins to retract comments they made about the ACC minister.
Collins claims she was defamed by Mallard and Little on Radio New Zealand when they raised questions about her role in the case of ACC claimant Bronwyn Pullar.
She has served Mallard, Little and Radio New Zealand with defamation papers.
Collins gave the opposition MPs until 5pm to withdraw their comments, but the deadline has passed without a word from them.
MPs can say what they like inside the House without fear of legal action, but Collins claims the interview on Morning Report today falls outside privilege and defamed her.
"I take my reputation very seriously and when I've been defamed I have to take action," Collins told Radio Live host Marcus Lush this morning.
"People need to tell the truth and they need to be very careful about what statements they make about other people."
Mallard said he was "absolutely certain" that Collins is serious about taking action, but added: "We'll see how she feels about that next week."
Labour says the ACC minister is using the defamation action and an investigation by the Privacy Commissioner into how the information was leaked as a way to fend off further questioning.
Radio New Zealand said it is now talking to its lawyers, as are the Labour MPs who say they will pay for lawyers out of their own pocket.
Collins is refusing to say if the taxpayer will be picking up her bill.
Prime Minister John Key said he supported Collins' legal action.
"I'm more than happy for her to do that. She feels very strongly about it - I can understand why - she's got nothing to hide and she feels she's been defamed," he said.
Collins said she is welcoming an investigation launched by the Privacy Commissioner into a leaked email sent to her from former National Party president Michelle Boag.
The email contained information about ACC claimant Bronwyn Pullar, but Collins and ACC management have denied leaking it to the media.
Collins told Radio Live she does not know who leaked the email and said she is "very careful about documents in my office".
Pullar was inadvertently sent an email from an ACC employee which contained the private details of 6700 ACC claimants, including victims of sexual abuse and other violent crime.
The leaked email had Boag's account of a December meeting where she and Pullar met with ACC management to discuss the privacy breach.
Pullar claims she promised not to divulge the personal details.
The new investigation could include forensic scrutiny of computers used by Collins and her staff.
Collins said she would be "very happy" for her computer to be examined.
Meanwhile, Labour is continuing to question the Government on who knew about the email.