Kate Middleton's family have contacted the Press Complaints Commission (PCC) to raise concerns about alleged "harassment" by photographers.
The BBC understands it follows incidents where Miss Middleton's mother and sister have been followed by agency photographers on mopeds.
The press watchdog has sent an advisory notice to editors reminding them of their ethical obligations.
It comes ahead of Prince William and Miss Middleton's wedding on 29 April.
BBC royal correspondent Peter Hunt said Carole Middleton and her daughter Pippa had also been followed by photographers on foot.
The Middletons have not made an official complaint to the press watchdog but the organisation has sent an advisory to newspaper, magazine and broadcast editors to remind them of their obligations under the editors' code of practice.
The code, which sets the benchmark for ethical standards in the press, states: "Journalists must not engage in intimidation, harassment or persistent pursuit."
A St James's Palace spokesman said: "No formal PCC complaint has been made by the Middleton family about any breaches of the editors' code.
"However, following some incidents of alleged harassment and pursuit by agencies and freelancers, the Middleton family, through the PCC, have sought to draw the attention of editors to their concerns.
"The Middleton family and St James's Palace remain grateful to editors for their restraint and adherence to the code over the past few months."
The spokesman added that they would take a "hard line" if any photographic agency pursued or harassed the royal couple.
A PCC spokesman would not discuss the details of the advisory, only saying it related to specific concerns.
"In this case we can confirm the Middleton family did contact us through representatives and we did send out a private advisory notice on April 6 advising editors to be aware of their obligations under the editors' code of practice," he said.
Since meeting the prince at St Andrews University in 2001, Miss Middleton has had a fraught relationship with the media.
In October 2005, after the publication of a photo showing Miss Middleton looking out of a window on a London bus, her lawyers wrote to newspaper and magazine editors asking them to respect her privacy.
Rumours of an engagement reached a peak around the time of Miss Middleton's 25th birthday in January 2007, when the media scrum took up residence outside her Chelsea home.
The paparazzi free-for-all drew inevitable comparisons with the prince's late mother, killed in a car crash in Paris while being pursued by photographers.
Prince William and Prince Charles appealed for Miss Middleton to be left alone, and some newspapers agreed to stop using paparazzi shots of her.