The royal family says it has a right to privacy in everyday private activities
The Queen has issued a strong warning to newspapers not to publish paparazzi pictures of the Royal Family.
Her lawyers have reminded papers of their obligations under the industry's own code of practice amid concern about invasions of privacy.
Photographers will be monitored on public roads around the Sandringham estate in Norfolk this Christmas.
Prince Charles's spokesman said the Royal Family had a right to privacy during "everyday private activities".
The Prince of Wales's spokesman Paddy Harverson said: "Members of the Royal Family feel they have a right to privacy when they are going about everyday, private activities.
"They recognise there is a public interest in them and what they do, but they do not think this extends to photographing the private activities of them and their friends."
In the past freelance photographers have spent many hours touring Sandringham to try and "snatch" pictures of the family on the estate.
Ingrid Seward, editor in chief at Majesty magazine, said it had become "very intense" over the past few years.
"They all want a picture of William and Kate out shooting, and not necessarily for the British papers, but, you know, these pictures make a lot of money abroad."
Prince William has expressed concern after he and Kate Middleton were "aggressively" pursued by the paparazzi in 2007.
And some still blame the paparazzi for their role in the death of Diana, Princess of Wales, in a Paris car crash a decade earlier.
BBC royal correspondent Peter Hunt said legal action, possibly on the grounds of harassment, was a long way off but could be taken if the royal appeals are ignored.
He said: "This is very much a warning shot across the bows. After years of turning a blind eye, senior royals have decided to take a more robust approach to what they see as unjustified intrusion."
Graham Smith of the anti-monarchy campaign group, Republic, said the Royal Family must remain open to scrutiny.
"Given the high level of secrecy already surrounding the monarchy the press must be allowed to pursue stories and take photos if there is genuine news value or public interest," he said.
The Royal Family "routinely use the media" and so they "cannot have it both ways", he added.