Prime Minister John Key said the decision was made solely by the Maori King's advisers, but the King's office made no comment.
"My understanding is the palace offered King Tuheitia's people an opportunity for the Prince to visit. They were offered a 90-minute slot. That was longer than pretty much any other engagement they have and King Tuheitia's people decided that wasn't long enough and on that basis, they rejected him actually attending."
It is understood the slot would not be long enough for proper protocol to be carried out during the visit.
Mr Key said: "It's a matter for them to decide their own thing, but in the end [Prince William] has a fairly tight timetable ... I would have thought [90 minutes] was quite generous.
"I think it's a shame he's not going, but that was a decision solely made by King Tuheitia's people."
The royal visit, from April 7 to 16, will be the Duchess' first trip to New Zealand and Prince George's first big appearance abroad. The Queen has given special permission for both heirs to the British throne to travel on the same aircraft, as royal protocol usually dictates that direct heirs travel separately.
Prince George - whose first royal tour mirrors the trip made by his father with Charles and Diana, the Prince and Princess of Wales, in 1983 - will be accompanied by a full-time nanny, currently being recruited.
Aides have arranged a "hub and spoke" travel plan for the tour, based on the couple's desire to spend as much time with their son as possible.
Visitors' schedule
April 7: Wellington: Arrive at Wellington Airport and receive ceremonial welcome at Government House.
April 8: Day off.
April 9: Plunket Parents' Group, Government House, Wellington.
April 10: Blenheim: Wreath-laying at war memorial and visit to World War I aviation commemorative event at Omaka Aviation Heritage Centre, accompanied by film-maker Sir Peter Jackson; State reception at Government House in Wellington with Prime Minister John Key.
April 11: Auckland: Meeting with air force personnel, yachting on Waitemata Harbour, ride in amphibious vehicle.
April 12: Waikato: Duke visits Pacific Aerospace, Duchess visits Rainbow Place Children's Hospice in Hamilton. Couple both visit war memorial in Cambridge, then open Avantidome velodrome in Cambridge.
April 13: Dunedin: Church service and visit to touch rugby tournament at Forsyth Barr Stadium. Queenstown: Visit to Amisfield winery and Shotover Jet white water ride.
April 14: Christchurch: Event to commemorate 185 victims of 2011 earthquake; couple play cricket to help publicise 2015 Cricket World Cup, visit to Wigram Air Force Base.
April 15: Day off.
April 16: Wellington: Royal New Zealand Police College visit, walkabout in city. Leave for Australia.
- additional reporting: Telegraph Group Ltd
