Simon Bridges says he stands by his description of a six-year National party veteran as an "emotional junior staffer".
In the hours following the Christchurch attack, a petition against the UN Global Compact for Migration was removed from the party's website.
The international agreement's aim is to coordinate migration policy worldwide, but it's non-binding and has no effect in law. The Government signed New Zealand up in December.
In the days leading up to the attack, the alleged Christchurch gunman uploaded photographs of weapons covered in names and slogans - one bearing the phrase, "Here's your migration compact".
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Bridges initially said the petition had been removed from the website weeks earlier, then when shown it was still live on the afternoon of the attack, claimed it had been removed hastily by an "emotional junior staffer".
But it later emerged the person who removed it was a former ministerial press secretary who'd been working with the National Party for six years.
Asked on Monday whether he'd still characterise him as an "emotional junior staffer", Bridges stonewalled.
"I stand by what I've said, but I'm not going to characterise it or get into it," he told host Ryan Bridge.
Asked to explain the word "junior", Bridges gave a flat "no".
"I'm not going to talk about employment matters."
As for whether it cast doubt on his ability to lead National, Bridges said he was doing "fine".
"I think we're working towards winning the next election."
The latest Reid Research poll put Labour on a commanding 49.6 percent and National on 41.3. With both of Labour's partners NZ First and the Greens falling below the 5 percent threshold, Labour would win enough seats to govern alone. National would be about seven seats short.