One of America’s leading Catholic bishops has described President Obama’s order last week to the US Department of Justice to stop defending the Defence of Marriage Act (DOMA) in US federal courts as an “alarming and grave injustice”.

Archbishop Timothy Dolan of New York has said in a statement that government had a duty “to recognise and protect marriage, not tamper with and redefine it, nor to caricature the deeply held beliefs of so many citizens as ‘discrimination’”.

President Obama repeatedly said during his 2008 election campaign that he believed marriage should be limited to a man and a woman. However, he and his Attorney General Eric Holder say they now believe it amounts to illegal discrimination.

Archbishop Dolan of New York, president of the United States Conference of Catholic Bishops (USCCB) said that traditional marriage was “a singular and irreplaceable institution”.

Archbishop Dolan said: “Only a man and a woman are capable of the “two-in-one-flesh” union of husband and wife.

“Only a man and a woman have the ability to bring children into the world. Along with that ability comes responsibility, which society historically reinforces with laws that bind mothers and fathers to each other and their children.

“This family unit represents the most basic and vital cell of any society, protecting the right of children to know and be known by, to love and be loved by, their mother and father. Thus, marriage represents the bedrock of the common good of society, its very foundation and future.

Criticising Attorney General Holder, he said the Act did not “single out people based on sexual ‘orientation’ or inclination”.

“Every person deserves to be treated with justice, compassion, and respect, a proposition of natural law and American law that we as Catholics vigorously promote. Unjust discrimination against any person is always wrong.

“But DOMA is not ‘unjust discrimination’; rather, it merely affirms and protects the time-tested and unalterable meaning of marriage. The suggestion that this definition amounts to ‘discrimination’ is grossly false and represents an affront to millions of citizens in this country.”

The decision of President Obama’s Department of Justice did not “stand the test of common sense” Archbishop Dolan added.

Believing that a husband and a wife had a unique and singular relationship that two persons of the same sex do not and cannot have was not discrimination, he said.

Nor was it discrimination to believe that the union of husband and wife had “a distinctive and exclusive significance worthy of promotion and protection by the state,” Archbishop Dolan said.

“It is not ‘discrimination’ to say that having both a mother and a father matters to and benefits a child.

“Nor is it “discrimination” to say that the state has more than zero interest in ensuring that children will be intimately connected with and raised by their mother and father.”

Protecting the definition of marriage was “not merely permissible, but actually necessary as a matter of justice,” he insisted.

Laws affirming the vital importance of mothers and fathers and which reinforced the ideal that children should be raised by their own mother and father—were essential for any just society, Archbishop Dolan continued.

He added: “Those laws serve not only the good of the spouses and their children, but the common good.

“Those laws are now under relentless attack. If we forget the meaning of marriage, we forget what it means to be a human person, what it means to be a man or a woman.

“The Administration’s current position is not only a grave threat to marriage, but to religious liberty and the integrity of our democracy as well.”