A SPERM donor in Kansas is fighting a state effort to force him to pay child support for a child conceived through artificial insemination by a lesbian couple.

William Marotta, 46, told The Topeka Capital-Journal he's "a little scared about where this is going to go, primarily for financial reasons".

When he donated sperm to Angela Bauer and Jennifer Schreiner in 2009, Mr Marotta relinquished all parental rights, including financial responsibility.

When Ms Bauer and Ms Schreiner filed for state assistance this year, the state demanded the donor's name so it could collect child support for the now three-year-old girl.

The state contends the agreement between Mr Marotta and the women is not valid because Kansas law requires a doctor to perform artificial insemination.