The image was circulated by a number of picture agencies on Sunday before Reuters, Associated Press (AP), Getty Images and Agence France-Presse (AFP) told media outlets to "kill" the photo from their systems and archives.

AP has told Sky News the photo shows an "inconsistency in the alignment of Princess Charlotte's left hand".

The picture in question was released to celebrate Mother's Day and shows Kate surrounded by her and Prince William's three children: Prince George, Princess Charlotte and Prince Louis.

Kensington Palace has declined to comment after the photo was pulled by picture agencies.

AP told Sky News in a statement: "The Associated Press initially published the photo, which was issued by Kensington Palace. The AP later retracted the image because at closer inspection, it appears that the source had manipulated the image in a way that did not meet AP's photo standards.

"The photo shows an inconsistency in the alignment of Princess Charlotte's left hand."

Reuters said it withdrew the picture following a "post-publication review" with a spokesperson saying the agency is "reviewing the matter".

Meanwhile, AFP said it had "come to light" that the image of the "Princess of Wales and her kids had been altered" and was therefore removed from its systems.

A spokesperson for Getty Images told Sky News: "Earlier today our picture desk identified a problematic image provided to Getty Images by Kensington Palace. We can confirm the image in question was removed from our site in accordance with our editorial policy."

The Press Association news agency did not initially pull it but on Monday morning said: "Like other news agencies, PA Media issued the handout image provided by Kensington Palace of the Princess of Wales and her children in good faith yesterday.

"We became aware of concerns about the image and we carried a report about it last night, and made clear that we were seeking urgent clarification about the image from Kensington Palace.

"In the absence of that clarification, we are killing the image from our picture service."

Readers on X, formerly known as Twitter, added a community note to a post from the Prince and Princess of Wales' account which shared the image.

Community notes allow readers to add context to posts to help other users have a better understanding of what they are reading or viewing.

The original note reads: "This photo is believed to be digitally altered and as a result many major news outlets have pulled the image from their reports."

The editing of photographs after they have been taken for professional purposes is a common practice, and there is no suggestion Kensington Palace was trying to do anything other than improve the photo if it has been altered.

However, without an official response from the palace, the confusion around the image is likely to fuel online conspiracy theories about Kate which have swirled on the internet since her abdominal surgery.

There has been speculation about Kate's health since she spent a brief period in hospital in January. She has not been seen in public since she joined other members of the Royal Family for a walk on Christmas Day.

Details of the princess's condition have not been disclosed but Kensington Palace previously said it was not cancer-related and that Kate wished her personal medical information to remain private.

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Speaking about how reports the Mother's Day image was altered might add to further speculation, royal commentator Peter Hunt said: "This is damaging for the royals.

"They knew there would be intense interest in any picture they released of Kate.

"Their challenge is that people will now question whether they can be trusted and believed when they next issue a health update."

Kensington Palace had provided the photo to agencies and said it had been taken by the Prince of Wales in Windsor earlier this week.

In a message accompanying the photo on Instagram, Kate, wrote: "Thank you for your kind wishes and continued support over the last two months.

"Wishing everyone a Happy Mother's Day."

The Prince and Princess of Wales's Instagram post featuring the image has not been taken down.

Kate was admitted for planned abdominal surgery on 16 January, exactly a week after her 42nd birthday.

The following day, the palace said the operation was successful and Kate stayed in hospital until 29 January, when she was discharged home to Windsor.

At the time, Sky News understood that her recuperation would likely take between two and three months.

Although Kate has not been seen in public since December, US celebrity news site TMZ published a photo of her on 4 March.

The photo was understood to have been taken by unauthorised paparazzi near Windsor Castle.

Kate is not expected to return to official duties until after Easter, and William, 41, had temporarily stepped back from his royal role to juggle caring for her and their children.

He carried out his first public engagements since her surgery in early February.