The comments are a reference to criticism of Ardern for donning a hijab following the Christchurch mosque attacks on March 15.

But Plunket has lashed out at her, saying her comments were an "offensive, nasty, ignorant thing to say".

"I, like many New Zealanders, believe that our Government and our Prime Minister acted incredibly well, incredibly graciously, and incredibly positively," he said on his Magic Talk show on Tuesday.

"Katie Hopkin's attack on our Prime Minister was unjustified, but her snarky sarcastic extremist tweet after the Sri Lanka bombings isn't just an attack on Jacinda Ardern, it is an attack on New Zealanders.

"She's a failed soldier, a failed talk host, a failed celebrity and a failed human being. She is a successful online troll, racist, Islamophobe and xenophobe."