NSW Premier Dominic Perrottet has admitted to wearing a Nazi uniform to his 21st birthday in 2003.
The 40-year-old said his costume choice for the fancy dress party was a grave mistake.
"When it was raised with me - this difficult truth of a grave and terrible mistake that I made at my 21st birthday party - to be told by someone else, I felt it was very important that it came from me," he told reporters on Thursday.