Prime Minister John Key will make a public apology if new information about Justice Minister Judith Collins emerges and forces her out of the job this week.

Mr Key made the promise on TVNZ this morning in response to a claim made by New Zealand First leader Winston Peters.

"Judith Collins will not survive next week with what I know," Mr Peters said during a debate on the network's Marae programme yesterday.

Ms Collins has taken stress leave following heavy criticism over her links with dairy company Oravida.

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Unanswered questions over a dinner between Ms Collins, Oravida bosses and an unnamed Chinese border control official late last year have fuelled the conflict-of-interest affair.

Today, Mr Key backed his minister.

"I will personally come into this studio if Winston Peters is right," he told TVNZ.

"He won't be right, he's never right."

Ms Collins is due to return to Parliament for the Budget this week, before resuming leave.