The Duke and Duchess of Sussex, Prince Harry and Meghan Markle, insist that they had asked the Queen for permission to use her childhood nickname Lilibet for their baby daughter, Report informs via British media.
The couple issued legal warnings following a report by the BBC that the monarch had not been consulted about the use of the name.
The Queen was not asked by the Duke and Duchess of Sussex about naming their daughter Lilibet, a Palace source has told the BBC.
The source disputed reports in the wake of the announcement of the name that Prince Harry and Meghan had spoken to the Queen before the birth.
But a Sussexes' spokesperson insisted they would not have used the name had the Queen not been supportive.
They said the monarch was the first family member the duke had called.
The spokesperson said: "The duke spoke with his family in advance of the announcement - in fact his grandmother was the first family member he called.
"During that conversation, he shared their hope of naming their daughter Lilibet in her honour. Had she not been supportive, they would not have used the name."
Lilibet has been the Queen's nickname among family since her childhood.
The relationship between the couple and the Royal Family has made headlines in recent months.
Earlier this year, while the couple were expecting their daughter, they aired criticisms of the Royal Family and made an allegation of racism in an explosive interview with Oprah Winfrey.
At the weekend, the couple announced that Lilibet "Lili" Diana Mountbatten-Windsor had been born at a hospital in Santa Barbara in California on Friday morning.
The name "Lilibet" is heavy with personal history for Her Majesty.
The nickname was coined when then-Princess Elizabeth was just a toddler and couldn't pronounce her own name properly. Her grandfather King George V would affectionately call her Lilibet, imitating her attempts to say her name. It stuck and came to be used by close relatives.
She signed her name as Lilibet on the funeral wreath for one of her closest friends Earl Mountbatten. The Queen's late husband, the Duke of Edinburgh, also called her by the nickname.