Swimming official, Cynthia Millen, has resigned in protest over rules that allow biological males to compete in female categories. Millen has been officiating meets in the US for 30 years.

“I can’t do this,” Millen wrote in her resignation letter, the Washington Examiner reported Thursday. “I can’t support this.”

Her move comes after male swimmer, Lia Thomas, competed as a woman, smashing records and beating his nearest opponent by a staggering 38 seconds.

“I told my fellow officials that I can no longer participate in a sport that allows biological men to compete against women,” Millen’s letter continued. “Everything fair about swimming is being destroyed.”

Thomas has been reducing his testosterone levels artificially but it still does not address the scientific reality that he has greater physical advantages than his female counterparts.

“Bodies swim against bodies,” Millen said. “Gender identities don’t swim.”

Men swim up to 12 percent faster than their female counterparts and have a greater lung capacity, the veteran swimming official said.

Thomas’ times in the water are now approaching records set by all-time Olympic greats like Katie Ledecky and Missy Franklin, Millen said.

“And nothing that Lia did by taking a year off to take testosterone suppression drugs — that does not change Lia’s body,” Millen said.

“This is grossly unfair.”

Binary spokeswoman, Kirralie Smith, agreed.

“Males appropriating womanhood in competitive sports are cheats,” she said.

“There are separate categories for males and females because males have a distinct advantage when it comes to size, strength and stamina.

“Feelings do not change biological reality. It is unfair and must be opposed at every level.”