Proposals to redefine marriage are illegitimate because “neither Church nor State invented marriage, and neither can change its nature,” Cardinal Francis George (pictured), the Archbishop of Chicago, has said.

He was responding to an initiative in the US state of Illinois to legalise same-sex marriage.

An attempt is being made to move the proposal before a new session of the state legislature begins next week.

However the bill, sponsored by Democratic State Senator Heather Steans, failed to overcome its first obstacle on Wednesday when it did not attract enough support to get a first hearing as Senate Republicans blocked an effort to allow the measure to be considered by a committee, the Chicago Tribune reports.

In his weekly column in his diocesan newspaper, Catholic New World, Cardinal George said that “the nature of marriage is not a religious question”.

He said the State “ protects marriage because it is essential to family and to the common good of society”.

What was at stake in the debate over same-sex marriage, Cardinal George said, was the natural relationship between parents and children.

He said: “Children, even if they are loved and raised by those who are not their biological parents, want to know who their parents are, who are their natural family.

“No honest “study” has disproved what we all know. Stable marriage between a husband and wife has safeguarded their children, surrounding them with familial love and creating the secure foundation for human flourishing.

“This natural desire, already weakened in a seemingly more and more promiscuous society, will no longer be privileged in civil law. It will be no more ‘normal’ than any other ‘family’ arrangement. If the nature of marriage is destroyed in civil law, the natural family goes with it.”

Legalising same-sex marriage would also lead to its opponents being labelled as bigots, Cardinal George said.

“Those who know that marriage is a union between a man and a woman for the sake of family will carry a social opprobrium that will make them unwelcome on most university faculties and on the editorial boards of major newspapers.

“They will be excluded from the entertainment industry. Their children and grandchildren will be taught in the government schools that their parents are unenlightened, the equivalent of misguided racists.

“Laws teach; they express accepted social values and most people go along with societal trends, even when majority opinion espouses immoral causes.”

Meanwhile, in the UK, the head of the Catholic Church in England and Wales has urged Catholics there to write to their MPs “as soon as possible” to register their opposition to same-sex marriage legislation.

The Archbishop of Westminster, Vincent Nichols, warned that the new legislation would mean that children would no longer be taught “the true meaning of marriage” in schools if the legislation was passed, the Daily Telegraph reports.

The Archbishop wrote to all parishes in England and Wales calling on Roman Catholics to lobby their MPs.

In his letter the Archbishop said politicians should “resist the proposed redefining of marriage with all its likely consequences particularly in schools and in how children are taught about the true nature of marriage”.

He continued: “At this time, we look to our Members of Parliament to defend, not change, the bond of man and woman in marriage as the essential element of the vision of the family.

“I urge everyone who cares about upholding the meaning of marriage in civil law to make their views known to their Members of Parliament, clearly, calmly and forcefully.”