James Middleton
Pictures of James Middleton wearing a dress were circulated on Facebook.Facebook

Kate Middleton might well be having a few stern words with her younger brother James.

A set of pictures have emerged of the 26-year-old socialite that might prove somewhat embarrassing for the Duchess.

The candid images, which appeared on Facebook, included a picture of James at a Freshers' party at Edinburgh University, where he is seen wearing a navy-blue polka-dot dress, not unlike something you might find in Kate's wardrobe.

In another he is dressed in an inflatable sumo wrestler's costume, and then there are the images of him emerging from the sea in his trunks after a New Year's dip.

The fun images may well show the younger Middleton sibling's sense of fun and tomfoolery, and while it's not dissimilar to the kind of antics Prince Harry is known for, it might not go down so well with the royal in-laws.

James Middleton
James Middleton dresses as a sumo wrestler in an inflatable costume.Facebook

Prince Harry was famously photographed at a fancy dress party in a Nazi costume, for which he later apologised.

Last year he was reportedly chastised by the Queen for his naked antics in Las Vegas when he was caught on camera cavorting with a blonde holiday-maker.

James, who is dating former MTV host Donna Air, runs a successful baking company called Nice Cakes.