The tea was held in Prince Andrew's private quarters while Queen Elizabeth II and Prince Philip were away in Scotland on official business. While Beckham posted the photos Monday, it is believed their visit to Buckingham Palace took place several days earlier.
The former soccer star posted another photo hugging his daughter and wrote: "Happy Birthday to our special little young lady ... Such a special girl who brings so much joy and happiness into our lives."
The posts sparked outrage about the child of a celebrity receiving special treatment at the palace, which is funded by taxpayers.
In response, David Beckham defended the visit on his Instagram account clarifying that it was not in fact a birthday party for his daughter.
"Just to be clear this wasn't the palace opening the gates for Harper's birthday party, this was a tea party where us and other guests were invited so it was a beautiful thing to do with My mum, Harper plus a few school friends," he wrote on Instagram. “We were honored to be able to there... Beautiful tea party....”
A Buckingham Palace spokesperson confirmed to ABC News that the private event took place.
"From time to time members of the Royal Family who reside at royal residences invite guests to visit privately," the spokesperson said.
A royal source confirmed that any costs associated with the visit would be paid by the Duke of York privately. The Duchess of York, who has not been present at many official engagements with the royal family since her divorce from Prince Andrew, also came under fire for her involvement in the planning of the event. Her spokesperson declined to comment to ABC News.
While members of the royal family do host various events at the Royal Palaces, they are typically for charitable activities and official engagements. Buckingham Palace is a publicly funded royal residence paid for by the British taxpayers. Queen Elizabeth privately owns the residences at Sandringham and Balmoral.
"This was supposed to be a private event, but the Beckhams publicizing it on their public Instagram accounts was indiscreet and inappropriate and violated the protocol of those who get invited to Private events at the Palace," Robert Jobson, ABC News contributor and author of “The Future Royal Family” said.
Government leaders recently approved a nearly $500 million refurbishment of Buckingham Palace, which will be funded by taxpayers, and may have contributed to the outrage around the Beckham party in the U.K.
"Nobody begrudges David Beckham treating his daughter to a birthday party, but it is not appropriate for Buckingham Palace to become a private party venue for the rich and famous," Jobson added.
Both David and Victoria Beckham have been recognized for their contribution to British society with Investitures at the Palace. In 2003, Beckham received an OBE and several months ago his wife, fashion designer Victoria Beckham, received an investiture for her service to the fashion industry from Prince William.
David Beckham has also participated in a number of Prince William and Prince Harry's charitable activities and in 2010 said he considered them friends.