By Daniel Wiessner

Oct 1 (Reuters) - A Manhattan judge has awarded custody of a lesbian couple's 5-year-old daughter to the adoptive mother, instead of the biological mother.

The ruling appears to be the first time a New York judge has granted custody to a gay or lesbian adoptive parent over a biological one, according to the lawyer for the plaintiff in the case.

Family Court Judge Gloria Sosa-Lintner found that Allison Scollar, the adoptive mother and a real estate lawyer, was a "more responsible" parent than her former partner, Academy Award-winning television producer Brook Altman, who gave birth to the girl in 2006.

The judge said that Scollar provided the girl, who turns 6 on Tuesday, with a more stable environment and a strict routine, while Altman is "the freer spirit" who often canceled the girl's therapy appointments to take her to play dates.

"Although (Altman) is the biological parent, this does not give her an automatic priority over the adoptive parent," Sosa-Lintner wrote in a decision dated Sept. 20. "This is analogous to a father getting custody of his own child, where only the best interests of the child are paramount."

Scollar's attorney, Brett Ward of Blank Rome, praised the ruling.

"What the court said was, when there are two legally recognized parents in a custody battle, they are on equal footing regardless of how they became the legally recognized parent," said Ward.

The decision is particularly important in light of New York's status as the sixth and largest state to legalize gay marriage, Ward said.

But the decision is likely not the first of its kind in the country, as courts routinely grant custody based on the best interests of children, and not biology, said Arthur Leonard, a professor at New York Law School and an expert on sexuality and the law.

Altman and Scollar were together from 2004 to 2010 and never married.

In July 2010, Altman allegedly took the daughter to California without Scollar's permission, the court said. Scollar obtained a court order requiring Altman to return the girl to New York, and the women then engaged in two years of "intensive" litigation over custody, Sosa-Lintner said. The case, which involved 27 court appearances, culminated in a trial in March.

Altman and Scollar disagreed over the level of involvement that the girl's father -- a gay man who was friends with the couple -- should have in her life, and "it seemed the biological parents were united in trying to alienate" Scollar, the judge wrote in awarding custody to Scollar.

Altman's attorney, Aimee Richter, did not immediately respond to a request for comment.

Scollar, a partner at Gold Scollar Moshan, said in an email that the decision was important for all adoptive parents.

"No longer shall we live in fear that the biological parent can assume superior rights," she said.

The case is Allison Scollar v. Brook Altman, New York State Family Court, New York County. No. V-17408/10.

For Scollar: Brett Ward and Marilyn Chinitz of Blank Rome.

For Altman: Aimee Richter of Bender Rosenthal Isaacs & Richter.

For the child: Rosemary Rivieccio.

Follow us on Twitter @ReutersLegal | Like us on Facebook