Judith Collins has defended her boss' use of the word "embarrassing" to describe a fellow MP's health problems.
Botany MP Jami-Lee Ross is taking time out from Parliament to deal with "personal health issues", National Party leader Simon Bridges announced on Tuesday.
But he went on to describe the issues as "embarrassing, potentially", reportedly angering Mr Ross. Mr Bridges on Thursday said he regretted his "poor choice of words".
But Ms Collins, whom Mr Bridges beat in the race to become leader of the party earlier this year, told The AM Show on Friday she wouldn't "second-guess" her leader.
Asked if Mr Bridges made a "misstep" in calling the health issue "embarrassing", she said no.
"Simon's got a lot more information on this than me, and I back him on this. I'm not going to go and second-guess people. It's very easy to second-guess, but I don't have that information and I'm absolutely backing him.
"He's been dealing with what is obviously a difficult situation. I don't know all the detail, and I don't want to pry into any of that."
If she was leading the party, Ms Collins wouldn't rule out using the same word.
"I don't know, because I don't have all the details Simon has. I really don't. I think it's a difficult situation and he's done his job."
There has been speculation Mr Ross was the one who leaked Mr Bridges' expenses in August, triggering a manhunt inside the National Party which is ongoing. Mr Bridges says he still doesn't know who the culprit is, but insists Mr Ross' leave isn't related.
Labour MP Michael Wood, appearing alongside Ms Collins, said MPs "as colleagues and human beings" should leave Mr Ross alone so he can concentrate on getting better.
"The question is about Simon Bridges' judgement and leadership in this matter. He's created a huge furore out of something that, if it was competently managed, would have blown over in a couple of days."
Mr Wood's comments echoed those of political commentator Trish Sherson, who told The AM Show on Thursday he should never have launched an inquiry into who leaked his expenses.
"Bridges handled it perfectly [on] day one. When those expenses were leaked he came out and said, 'Hey - I was doing my job.' It didn't seem to have anywhere to go, the story died pretty quickly, and then [came] the whole decision around going after who leaked it. That's just taken on a whole life of its own."
Prime Minister Jacinda Ardern said she would not have used the word "embarrassing" to describe an MP's health issues, and Privacy Commissioner John Edwards said Mr Bridges "chose a word unwisely".