Headlines from media outlets summed up the outrage from the left, with the U.K.'s Daily Mirror proclaiming, "Outrage as Prince George plays with toy and knife on family day out amid surge in violence", and several citing quotes from Twitter users such as, "sad to see him playing with a gun when the United Kingdom has a crime problem".
"Completely tone deaf of Kate.to give Prince George a toy gun".
One person wrote: 'This was the only disappointing thing about today's polo match photos.
Charlotte attempted headstands and pranced around the grounds, much to the amusement of her mother, who could be seen having a hearty laugh while her daughter was upside down. Malcolm is said to have a close relationship with the Royal Family and has played alongside Prince Harry at the Sentebale Charity Cup.
The match, which will see the Maserati team take on the Dhamani 1969 side, is part of the two-day Gloucestershire Festival of Polo, hosted by Beaufort Polo Club from 9th-10th June. He and Kate also spent time playing with a rainbow slinky.
On Saturday, the British royal family gathered on the Buckingham Palace balcony for a grand parade and air show to mark Queen Elizabeth's official 92nd birthday.
A shy Prince George, four, looked on as his outgoing sister Princess Charlotte, three, attempted hand stands, and Kate was seen getting stuck in as she rand around playing with the youngsters.
Another tweet said it wasn't acceptable for Prince George to be playing with toy guns as people had died in incidents where children ostensibly played with toys which turned out to be real guns.
There was no sign of Prince Louis, who was born last month.