TOKYO >> Japanese Prime Minister Fumio Kishida said Monday his son is resigning as his executive policy secretary to take responsibility for using the prime minister’s residence for a private party at which the merrymaking was exposed in magazine photos that triggered public outrage.

Shotaro Kishida, his father’s executive secretary for political affairs and eldest son, invited a group of people including relatives to a year-end party on Dec. 30 at the Prime Minister’s Official Residence.

Photos published by the weekly Shukan Bunshun magazine showing Kishida’s son and his relatives posing on red-carpeted stairs in an imitation of the group photos taken of newly appointed Cabinets, with his son at the center — the position reserved for the prime minister. Other photos showed guests standing at a podium as if holding a news conference.

“As secretary for (the prime minister’s) political affairs, a public position, his actions were inappropriate and I decided to replace him to have him take responsibility,” Kishida told reporters Monday night. He said his son will be replaced with another secretary, Takayoshi Yamamoto, on Thursday.

Kishida acknowledged that he had briefly greeted the guests but said he didn’t stay at the dinner party.

He said he severely reprimanded his son for the party, but that failed to quell ongoing criticism from opposition lawmakers and public outrage which have pushed down his support ratings.

Kishida appointed his son as policy secretary, one of eight secretary posts for the prime minister, in October. The appointment, seen as a step in grooming him as his heir, was criticized as nepotism, which is common in Japanese politics, long dominated by hereditary lawmakers. His son was previously his father’s private secretary.

It was not the first time Kishida’s son has come under fire for making use of his official position for private activities. He was reprimanded for using embassy cars for private sightseeing in Britain and Paris and for buying souvenirs for Cabinet members at a luxury department store in London when he accompanied his father on trips.

Chief Cabinet Secretary Hirokazu Matsuno earlier called the son’s party at the official residence “inappropriate” and promised to ensure proper management of the facility to prevent future misuse.

The nearly 100-year-old building previously was the prime minister’s office and became the living quarters in 2005 when a new office was built.