Letters signed by the couple's spokesman warning the paparazzi were handed out to the media by Norfolk Police, British media reported on Thursday.
PHOTO: HELLO!MAGAZINE
It was quoted as saying that while the Duke and Duchess of Cambridge are in residence they have "a more than reasonable expectation of privacy".
The letter called for "acts of harassment" to end.
"There have in the past been a number of intrusions into the privacy of the Royal Family which in the main have been as a result of professional photographers using long-distance lenses," it added.
Kate gave birth on Saturday and the royals named their baby Princess Charlotte Elizabeth Diana - the middle name is a tribute to her great-grandmother Queen Elizabeth II and William's much-loved late mother.
Diana was killed in a crash in a road tunnel in Paris in 1997 as her car was being chased by photographers.
William is said to have harboured resentment against media intrusion from that time when he was just 14.
In 2012, Closer magazine published topless photos of Kate while she and William were on holiday in France.
Pictures of the couple sunbathing on the terrace of a private villa were taken by a photographer using a powerful long-lens camera from public land.
The couple have already shielded their first child, Prince George born in 2013, from the cameras and earlier threatened to sue a photographer who followed their nanny as she took him to a park.
PHOTO: ROYAL-FANS
William and Kate traveled on Wednesday to their 10-room mansion in Norfolk, which is on the Queen's privately-owned Sandringham Estate.
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