Two Illinois county clerks have been granted permission to defend the state’s equal marriage ban.

The clerks, named as Effingham County Clerk Kerry Hirtzel and Tazewell County Clerk Christie Webb, are being backed by Catholic group The Thomas More Society, which filed a request on their behalf.

Twenty-five gay couples recently filed a lawsuit against the 16-year-old equal marriage ban and the state is refusing to defend it.

Last week, the attorney general of Illinois, Lisa Madigan, and Cook County’s state attorney, Anita Alvarez, both announced that they will no longer defend the anti-equality act.

Ms Alvarez said it violated the state constitution’s equal protection clause.

As Ms Madigan and Ms Alvarez have announced they will not defend the ban, the next step may see a judge striking it down. The move means gay rights opponents must make their own defence of the ban.

According to the Chicago Tribune, Peter Breen, the executive director and legal counsel for The Thomas More Society, said: “We will have a full and robust defence of the marriage law.”

The battle centres on the Defence of Marriage ACT (DOMA), which is no longer defended at a federal level by the Obama administration. However, some states continue to defend it.

Now, judges in several states such as New York and Massachusetts have moved to declare DOMA unconstitutional, and the law seems certain to be heading to the US Supreme Court.