Prince George is being increasingly targeted by paparazzi, the Duke and Duchess of Cambridge say, with London's Metropolitan Police warning those targeting the Royal family risk being shot.

In a strongly worded and detailed open letter sent to media organisations around the world, the Royal couple appealed to readers of magazines which published these unauthorised images to think about the methods used to attain them.

Prince William and Catherine, Duchess of Cambridge, said the "increasingly dangerous" tactics employed to get photographs of their young son included hiding in sand dunes, woodland and car boots, pursuing cars and using other children to entice the Prince into view at playgrounds.

The statement said an incident last week was disturbing, but not at all uncommon.

"A photographer rented a car and parked in a discreet location outside a children's play area. Already concealed by darkened windows, he took the added step of hanging sheets inside the vehicle and created a hide stocked with food and drinks to get him through a full day of surveillance, waiting in hope to capture images of Prince George," the letter said.

The letter said the Royal family hoped the publishers of unauthorised photos of children understood the power they held "to starve this disturbing activity of funding".

Sorry, this video has expired Royals appeal against 'dangerous' tactics to photograph Prince George ( By Europe correspondent Barbara Miller )

They have publicly appealed to media organisations not to print unauthorised photographs of their son.

The family expressed gratitude to British media organisations who they said did understand the severity of the matter, adding they were pleased that other Commonwealth publications — in particular in Australia, Canada and New Zealand — had adopted a similar position.

The Royal couple said they did not want their children to grow up behind Palace gates and in walled gardens but felt deep unease when they saw such images published.

London's Metropolitan Police soon after released a statement saying protection officers had to make split-second decisions, and photographers using covert tactics ran the risk of being mistaken for someone intent on doing harm.