Labour Party leader David Cunliffe is accusing the Prime Minister of stage managing events this year to give him an advantage at the general election on 20 September.
Mr Cunliffe has questioned why John Key gets to spend more time with visiting members of the Royal family than him, and why Mr Key has made plans for a possible White House visit later in the year.
Prince William, his wife Catherine the Duchess of Cambridge and their eight-month-old son Prince George arrived in New Zealand on Monday for a nine-day tour.
David Cunliffe believes the visit should should be as evenly split as possible between the Government and the opposition, and suggested that Mr Key is tagging along with the Royals for the extra camera time.
On Thursday, Mr Cunliffe and John Key will meet with Prince William before a state reception is held.
Labour will also accompany the Royals to a craft museum in Blenheim, but Mr Cunliffe says Mr Key has considerably more time at their side - and he will leave it to the public to decide whether that is fair.
"I think the public will watch closely to see how the Prime Minister treats his presence on the tour in an election year so close to an election. As I say, our position is to welcome the tour and I look forward to meeting with the Duke and Duchess."
But John Key dismissed criticism that he's hogging the limelight, saying it's part of the job for the Prime Minister of the day to spend some time with visiting dignitaries.
"Well, we spent a long time where Helen Clark was the Prime Minister and we didn't necessarily get the same access that the Prime Minister of the day gets. The real only difference is I meet them in my formal capacity at the airport. David Cunliffe was there at the formal meeting at Government House yesterday."
David Cunliffe also took aim at Mr Key for a possible visit to the White House, which could occur before the general election on 20 September. However Mr Key said it's not going to make a difference to voters whether or not he meets President Barack Obama then.
New Zealand First leader Winston Peters said on Tuesday he would feel sorry for Prince George if he gets caught up in "subservient, photo opportunity behaviour" by politicians and believes it would have been better for the tour not to have taken place in an election year.
"The poor baby deserves a far better time in New Zealand than that, and I just would hope that we don't see this obsequious, subservient, photo opportunity behaviour. You can guarantee I won't be part of it."