One of the largest adoption websites in the world is being sued for refusing to accept a listing from a gay couple.

Michael Butler and Richard Butler, who live in California, took action against Arizona-based adoption.com and its owners, Nathan and Dale Gwilliam, in December 2003.

The couple have finally been given permission by a judge to go to trial.

The website, which offers a service for birth parents to find couples who want to adopt their child, claimed it had a right under the First Amendment of the US Constitution to refuse the gay couple’s listing.

U.S. District Judge Phyllis Hamilton rejected that free speech argument.

Gay rights advocates said her decision to allow a trial was an important step forward.

Shannon Minter, legal director of the National Centre for Lesbian Rights, said that state laws which outlaw discrimination should apply to adoption.com

“They are the biggest internet company based on that service. They have a near monopoly.

“They do more business with people in California than any other state,” he told AP.