On Monday, Prime Minister Jacinda Ardern announced a service would be held in Wellington on April 21, beginning at 3pm local time.

Ms Ardern has also advised New Zealand's parliament will abandon its planned business on Tuesday this week and instead debate only a notice of motion commemorating the life of the Duke of Edinburgh.

"Our thoughts continue to be with Her Majesty the Queen, and the royal family at this time," she said.

Earlier on Monday, Ms Ardern signed a condolence book in tribute to Prince Philip.

She wrote, "With deepest sympathy and gratitude for a life of service" and a note in te reo Maori.

Ms Ardern defended putting the memorial service on the 95th birthday of the monarch.

"No one wants anyone to be in a state of grief at the time of their birthday," Ms Ardern said.

"But New Zealand has an obligation to make sure that we respectfully do not hold the memorial before the funeral but ... not wanting to wait too long after the official funeral."

Flags will fly at half-mast on Tuesday for parliament's considerations and again next Wednesday.

While the Duke of Edinburgh's death is being discussed with an appropriate reverence in New Zealand, many are not mourning.

Prince Philip is seen by many Kiwis as a part of New Zealand's colonising family, and with his own record of racist statements.

Asked about the legacy the 99-year-old leaves, Ms Ardern suggested the memorial service will steer clear of "challenging elements".

"Through our history we will have challenging elements to the foundation of our history," she said.

"Now also offers an opportunity for us to acknowledge the contribution of someone who ultimately - no matter what anyone's opinion will be - gave his entire life to the service of others."

Australian Associated Press