Happier times: The Queen and Kate are currently at odds, according to reports Getty

The mother-in-law relationship is, for many, one of the most complicated, tricky family ties ever experienced.

Indeed, as is life for commoners, so goes it for the highest in the land, with Kate Middleton, the Duchess of Cambridge, reportedly feeling the full force of family dysfunction in an increasingly tense relationship with mother-in-law Number One, aka The Queen.

Traditionally, Christmas is the time for family flare-ups and the British royal family is reeling from the mother-of-all rows amid reports that Kate is now in full-on feud mode with Queen Elizabeth.

According to Life & Style magazine, the Duchess of Cambridge's allegedly turbulent relationship with the monarch came to a head over the festive season after she decided to snub the annual Sandringham Estate (the Queens' country residency in Norfolk) gathering and celebrate Christmas with her parents, siblings and Prince William at their nearby country home, Anmer Hall.

The Queen was allegedly left fuming and even accused Kate of breaking "decades of protocol".

"The Queen wanted Kate, William and George to have Christmas lunch with her, as they traditionally do... [But] Kate put her foot down and said she was eating with the Middletons instead," a source told the magazine.

While the Daily Mail reported that the Duchess of Cambridge ditched the Queen's gathering because the dining room at Sandringham simply isn't large enough to fit all the Middletons, Life & Style claims that her grandmother-in-law flat out refused to accommodate non-royal family members.

"She's banned the Middletons from staying at Sandringham even though she has plenty of room for them," said an insider. "She almost ruined Christmas for Kate."

Kate Middleton
The Duchess met with 20 awards finalists, including children from Highfield Community Primary School in Sunderland AFP / Getty Images

Weight gain comment

The tabloid adds that despite the Queen extending an olive branch by inviting the Middletons to visit on Boxing Day, she is still in Kate's bad books after allegedly commenting on her weight during her second pregnancy.

"The Queen has told Kate to gain weight, but Kate says she would if she could!" said a source, referring to the Duchess' previous battle with hyperemesis gravidarum, an acute form of morning sickness. "The constant nagging is not helpful."

Although the palace has not commented on the alleged feud, last summer it was reported Kate was at odds with Queen Elizabeth over her plans to relocate out of London with 17-month-old George and Prince William. The October Life & Style magazine also reported that Her Majesty "commanded" the pregnant Duchess to return to work, despite her morning sickness.

The stories contradict other reports that the royal duo get on like a house on fire.

"The Queen regards Catherine as the perfect partner for William and she thinks they are a great team," an insider previously said.

"She doesn't want to see a repeat of Charles and Diana when they toured Australia and the crowds were only interested in meeting Diana.

"Most importantly, the Queen can pass on her knowledge of the countries, their cultures, histories and the dos and don'ts of what to say and not say."