KOBE (Kyodo) A Hyogo Prefecture man who has legally changed his sexual status said Sunday that the city where he lives told him to register his son, who was born through artificial insemination, as an illegitimate child.

Children born through artificial insemination by donors are ordinarily accepted as legitimate, experts say, because municipal offices do not necessarily know the details of a particular birth.

But in the man's case, the municipal office knew he had changed his sex in his family registration record, apparently leading it to reject the legitimacy of his son, they said.

"This man is lawfully married. It is discriminatory not to recognize him as the father," said Toshiyuki Oshima, a Kyushu International University professor and head of the Japanese Society of Gender Identity Disorder.

The man, whose name is being withheld, is a 27-year-old resident of Shiso, Hyogo Prefecture. He received approval for the sex change under a special law concerning people with sexual identity disorder and changed his family registration record to reflect it in March 2008. He married the following month.

On Nov. 4, 2009, his 28-year-old wife gave birth to the boy through artificial insemination using semen from the man's brother.

The man went to register the boy the following day but was unable to do so and later told by the municipal office to register him as adopted.

After getting legal advice, the man sent his son's birth report to the city office and is waiting for it to respond.

If his request is refused again, he will take the case to court, he said.

"I am recognized by the country as a man but not as a father. I wonder why the special law (for people with sexual identity disorder) exists."