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The Duke and Duchess of Cambridge are parents to Prince George and Princess Charlotte and speculation has been rife the proud parents could have another baby. But the royal couple have been told they should not have any more children in a letter written by ‘Having Kids’, an organisation that promotes smaller families. Citing environmental reasons like climate change, economic equality and the distribution of ‘resources’, the open letter urges Prince William and Kate to “consider forgoing having a third child… in favour of modelling a smaller, sustainable family.”

GETTY An open letter has urged the Royals not to have more children

GETTY Princess Charlotte is the fourth in line to the throne

The plea comes just days after 35-year-old Kate, hinted she would like to have another child after being handed a gift for a newborn during the couple’s recent royal tour of Poland and Germany. On accepting the gift from a well-wisher in Warsaw, the Duchess turned to her husband and said: “We will just have to have more babies.” Having Kids executive director Anne Green said: “William and Kate have a tremendous opportunity to model their choice of having a smaller family. “By doing so, they set an example as to what has the most potential for mitigating climate change and its impacts, including severe flooding, deadlier heatwaves, increase in diseases, and wildlife extinctions. “Moreover, given the vast economic inequalities in the world today, the couple also has the opportunity to model a simple principle: That every child deserves as fair start in life."

Princess Charlotte in pictures Mon, July 9, 2018 Princess Charlotte of Cambridge, Charlotte Elizabeth Diana, who was born on 2 May 2015. Play slideshow PA 1 of 100 Princess Charlotte in pictures

Acknowledging the couple's royal status, the open letter says: “We know that Prince George and Princess Charlotte are certain to have wonderful lives, protected from the deprivations of poverty and the threat of environmental degradation. “They will receive optimal amounts of care and attention, as well as the best possible education. “But the same can’t be said of every future child.” The letter echoes the company’s mission statement, published on its website, with the San Francisco-based organisation aiming to promote and protect “every child’s right to a fair start in life by replacing parent-centred family planning models with the child-centred Fair Start family planning model.”

GETTY Prince George turned four last weekend