However, the trip has been abandoned for career rather than political reasons, she said.
Reports in Britain's Daily Mail that the newly-titled Duke and Duchess of Cambridge had abandoned plans to visit New Zealand were labelled "pure speculation" by Prime Minister John Key on Sunday.
But the spokeswoman for the royal family told NZPA overnight the trip was definitely off.
"On the record, we can confirm the Duke and Duchess of Cambridge and Prince Harry were all very pleased and honoured to be invited, in a private capacity," she said.
"They have considered the matter, and with regret, they'll be unable to attend owing to their military pressures."
However, she said the decision to stay away did not to her knowledge have anything to do with avoiding New Zealand's general election shortly after the World Cup.
"The Duke of Cambridge will spend the autumn concentrating on his search and rescue career, as he builds up flying hours and passes the necessary examinations to allow him to obtain captaincy at some point in 2012, and Prince Harry's course at Wattisham and in the USA doesn't really afford him any time to attend," the spokeswoman said.
The Royal family do not traditionally visit Commonwealth countries during general elections, and the Daily Mail reported the decision not to visit was because they did not want to be involved in a political row.
Prince William, 29, who is an avid rugby fan and vice patron of the Welsh Rugby Union, visited New Zealand when the Lions toured in 2005.
After attending the couple's wedding in April, Mr Key told reporters he hoped they would visit "sometime very soon".
"The first thing Kate said to me was she wants to visit New Zealand," he said.
