Catherine, Princess of Wales on Monday apologised and admitted to editing an official portrait of her released by the palace, after AFP and other agencies withdrew the image.
Kate, 42, has not been seen in public since attending a Christmas Day church service, and underwent abdominal surgery in January, fuelling speculation about her health, particularly online.
Her Kensington Palace office on Sunday sought to dispel rumours by distributing an official photograph said to have been taken by her husband Prince William of her with their three children.
But questions quickly emerged of the Mother's Day portrait of a smiling Kate, casually dressed and seated in a garden chair, surrounded by Prince George, Princess Charlotte and Prince Louis.
Discrepancies included several inconsistencies, such as Charlotte's left hand being misaligned with the sleeve of her cardigan and a missing part of her sleeve.
The eight-year-old princess's hair ended abruptly on her shoulder while Kate's zip was lighter than elsewhere.
AFP, Getty, the Associated Press (AP) and Reuters all have policies about distributing manipulated images, and pulled it, despite initially publishing the photograph provided by Kensington Palace.
Britain's domestic Press Association said on Monday it, too, was withdrawing the image, noting "the absence of clarification" about the image from Kensington Palace.
Within minutes of PA announcing its decision, the palace issued a statement on X (formerly Twitter), signed by "C" for Catherine.
"Like many amateur photographers, I do occasionally experiment with editing," it stated.
"I wanted to express my apologies for any confusion the family photograph we shared yesterday caused."
- 'Damaging' -
Many commentators suggested the furore had cast fresh doubt on palace reassurances about Kate's health and recuperation.
William, 41, and other senior royals are expected to attend annual Commonwealth Day celebrations in central London later on Monday.
Peter Hunt, a former BBC royal correspondent, said the situation was "damaging" for the family. "They knew there would be intense interest in any picture they released of Kate," he said.
"Their challenge is that people will now question whether they can be trusted and believed when they next issue a health update."
Graham Smith, who heads the Republic pressure group calling for an elected head of state, added: "It's quite simple. Don't use their own photos. It's PR, not news."
Intense interest in Kate's absence comes from the fact that William -- King Charles III's elder son -- is heir to the throne, meaning she will be one day be queen.
According to Kensington Palace, she was admitted to hospital on January 16 for planned surgery, then left on January 29, to recuperate at home until at least Easter on March 31.
The contentious photograph, published on all royal social media channels and widely picked up in Britain and across the world, was accompanied a message signed by Kate.
"Thank you for your kind wishes and continued support over the last two months. Wishing everyone a Happy Mother's Day," it read.
But in a note to clients, AFP said it withdrawn the image after it had "come to light that the handout issued by Kensington Palace today of Kate and the kids had been altered".
The AP said it had retracted the image because on "closer inspection, it appeared the source had manipulated the image in a way that did not meet AP's photo standards". Reuters said similar.
- Health woes -
British newspapers quickly changed their front pages late on Sunday to reflect the brewing controversy.
Royal officials have not specified the nature of Kate's operation but have said it was not cancer-related.
Earlier this month, a snatched photograph said to have been of Kate wearing sunglasses while being driven by her mother were published on the celebrity news site TMZ.
The sighting, said to have been near William and Kate's Windsor home west of London, also failed to dampen conspiracy theories on social media about Kate's absence from the spotlight.
The announcement about Kate's hospital admission came just before another about her father-in-law's treatment for a benign enlarged prostate.
It was then announced that he had been diagnosed with an unrelated -- but so far unspecified -- cancer, which has forced him to cancel public engagements, barring some official meetings.
Charles, 75, has only been king and British head of state since the death of his mother Queen Elizabeth II in September 2022.
His wife, Queen Camilla, 76, has since stepped up to take the lead as the royals' most senior figure at public events.
By Joe Jackson
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