Two Republican representatives in Illinois, US, have introduced a joint resolution in support of the state’s ban on equal marriage.

David Reis and Thomas Morrison’s resolution says marriage should be restricted to heterosexual couples.

Mr Reis attacked attorney general Lisa Madigan, who has said her office will not defend the “unconstitutional” law against a challenge brought by 25 gay and lesbian couples.

He said in a statement: “It is time for the General Assembly to reaffirm their support for Illinois laws reserving the institution of marriage between one man and one woman.

“The people I represent are adamantly opposed to same-sex marriage and troubled by our attorney general’s recent dereliction of duty by not defending our state’s policy on marriage.”

Earlier this month, two Illinois county clerks were granted permission to defend the state’s gay marriage ban, as the attorney general’s office has refused to do so.

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.