The Catholic Archbishop of Chicago, Cardinal Francis George, has warned against introducing marriage equality in the state of Illinois because he claims gay couples cannot consummate their unions.

Over the weekend, President Obama encouraged politicians in his home state to change the law as part of a move by State Representative Greg Harris and Senator Heather Steans, both Democrats, from Mr Obama’s home city of Chicago.

The pair said they were close to securing enough support to bring their proposed marriage equality bill up for a vote, but won’t do so unless they are confident it will pass the Illinois General Assembly.

Horrified at the prospect, Cardinal Francis George of Chicago has warned against marriage equality.

“Marriage comes to us from nature”, said the cardinal, in a recent interview with the Chicago Tribune.

“That’s based on the complementarity of the two sexes in such a way that the love of a man and a woman joined in a marital union is open to life, and that’s how families are created and society goes along…It’s not in our doctrine. It’s not a matter of faith. It’s a matter of reason and understanding the way nature operates,” he said.

In a sign the cardinal realises he is a fighting a losing battle, he acknowledged that there is some “inevitability” to the bill’s introduction.

Responding to the cardinal’s comments, Bernard Schlager, executive director of the Center for Lesbian and Gay Studies in Religion and Ministry at Pacific School of Religion in California, said:

“On sexual ethics, nature is neutral. We’re moral beings. We may look to nature for some aspects of how we are in our lives, but we answer to a higher standard. Sexual behaviour is an expression of human love.”

Illinois legislators approved civil unions in December 2010.