Education Minister Hekia Parata says the Prime Minister's suggestion that her husband's ill-health played a part in her shock decision to retire from politics is wrong.
Parata is married to Sir Wira Gardiner, former director of the Waitangi Tribunal, with whom she has two daughters of university age.
This morning, Key told More FM that Sir Wira's ill-health may have played a role in Parata's decision - contradicting Parata, who yesterday said she and her close family were in good health.
"Firstly, being Minister of Education is tough but it's not really about that, because we could have put her in another portfolio," Key said on More FM.
"But her husband Wira Gardiner - who's a great man - but he's in his early 70s, he's had a couple of health issues recently.
"And I think it's a combination of, she came to a job and she's done a lot of what she [planned] - you never get the job done, but she's done a lot.
"And secondly I think she's really felt [in need of] a bit more of a work-life balance, I think."
This afternoon, Parata said Sir Wira was not suffering ill-health.
"My family, including my husband, are hale and hearty. I think the Prime Minister was referring to the fact that we all age, and clearly we all are ageing."
She said she wasn't disappointed in the Prime Minister's comments, and no apology was sought or necessary.
"I don't think it is a major at all, and certainly my husband is completely relaxed about the comments."
Yesterday, Parata said she made the decision not to contest next year's election after talking with her family last summer, and told Key early this year.
She would not reveal what her plans were after politics, saying she had no intention of seeking a diplomatic post. It will be the Prime Minister's call when she gives up the education portfolio.
Parata was elected to Parliament in 2008 and has served as Education Minister since 2011. Her departure is unexpected - she is currently overseeing the biggest education reforms since 1989.
Her biggest achievement to date and potentially her legacy has been getting through changes to enable and encourage groups of local schools to work together, with teachers and principals paid more to take a lead in those new "communities of learning".
Not as headline-grabbing as online schools or charter school expansions, the policy isn't particularly ideological either - it is similar to an earlier policy proposal from the Post Primary Teachers Association (PPTA).
Nonetheless, significant work and compromises were made to convince the secondary school union to cautiously back a key National policy in election year (the primary school union NZEI spoke out against the reform).
Parata has had her low moments in the portfolio, with most occurring in 2012 - the year she calls her annus horribilis.
That saw an embarrassing U-turn on plans to increase class sizes, a backlash against her handling of proposals to merge or close Christchurch schools, and the implementation of the disastrous Novopay school payroll system.
There was speculation that Key would dump her from the portfolio, but he backed her and she has been pushing through a raft of changes including clearing the way for online schools (COOLs) and an overhaul of the school and ECE funding, that will scrap the decile system.
One funding proposal to give schools a "global budget" has been strongly rejected by the education unions as a return to bulk-funding, sparking classroom disruption as the PPTA and NZEI held joint meetings across the country.
Before entering Parliament in 2008, Parata held a number of public servant positions including in the Ministry of Foreign Affairs and Trade and advising former Labour Prime Minister David Lange during the period when Tomorrow's Schools was developed and approved.
After Don Brash's Orewa speech on "special treatment" for Maori, Parata resigned her party membership and attacked the speech in a newspaper opinion piece.
She returned to the fold under John Key's leadership. Her maiden speech mentioned education five times. Three years later she took over the crucial portfolio from Anne Tolley.
Associate Education Minister Nikki Kaye's breast cancer diagnosis has seen Parata take on more work recently. Kaye would be the obvious choice to replace Parata, but for her ill-health.
• One of 10 siblings. Her brother and sister were brought up by relatives who were unable to have children themselves (whangai adoption).
• Involved in organising protests against the 1981 Springbok Tour.
• Quit National after former leader Don Brash's Orewa speech.
• Has been Education Minister since December 2011.