A lawsuit has been filed challenging the US state of Utah’s ban on equal marriage.

The brief, which was filed by the American Civil Liberties Union on Thursday, argued that a constitutional amendment, and other laws which discriminate based on sexual orientation should be scrutinised in court.

In a statement, ACLU legal director John Mejia, said that the laws stop loving, committed couples from the protection, and dignity, offered by the institution of marriage.

The brief comes just a week after Utah attorneys filed motions which defended the ban. In its defence they wrote that it protects the state’s “responsible procreation”, and the “optimal mode of child-rearing.”

The state’s defence of the bill noted that it was the most-married, and most “child-centric”, state in the US. It argued that it has the right to stand by an “age-old and still predominant” definition of marriage.

Utah Governor, Gary Herbert in August responded to a law suit challenging the state’s ban on same-sex marriage claiming that the current legal situation does not discriminate against same-sex couples.

In 2004 voters in Utah voted in a referendum to define marriage as a legal union between one man and one woman.