A judge in Cook County, Illinois, has ruled that a lawsuit challenging the state’s ban on equal marriage can proceed.

Judge Sophia Hall partially denied a defence motion to dismiss the lawsuit, saying that it could go ahead on two of the five counts filed.

Attorneys on behalf of the plaintiffs called the two counts their “primary counts”.

The lawsuit claims that the state’s same-sex marriage ban violates the due process rights of gay and lesbian couples and discriminates against them under the equal protection clause in the state, which protects against discrimination based on sexual orientation.

“It’s a victory in Illinois,” said Ed Yohnka of the American Civil Liberties Union of Illinois, one of the two groups that filed the lawsuit. “We needed this step to move on with the case.”

Attorneys acting on behalf of the Thomas More Society, a public interest law group defending the state’s ban said that the three counts dismissed by the court were a victory, and that they would allow it to focus efforts on the case.

“We’re glad for the partial dismissal,” said Thomas More Society attorney Peter Breen. “It gives us the opportunity to make our case that marriage between a man and a woman has great benefits, particularly for children. The case will proceed, but this will allow us to narrow our focus.”

The Illinois Senate passed a bill to remove the ban in February, but the bill’s sponsor in the House did not call it for a vote, as he said it did not have enough votes to pass.

Last month, opponents to equal marriage in the US state of Illinois celebrated the fact that the bill to legalise same-sex unions never went to a vote.

The bill’s sponsor Greg Harris wept as he announced that, due to a lack of support, the bill would not be voted on. Mr Harris said he planned to lobby for the bill before the next legislative session in the autumn.