The spiritual leader of Ireland’s Roman Catholics has said that civil partnerships undermine marriage.

Cardinal Sean Brady has expressed his disapproval of partnerships before.

Civil partnerships are already legal in Northern Ireland and there is legislation before the Republic of Ireland’s parliament to introduce them.

The Roman Cahtolic Church in Ireland has said it may support a legal challenge to new legislation.

In a sermon yesterday Cardinal Brady claimed Catholics, who make up 87% of the Republic’s 4.4m population, would have to choose to “stand clearly on the side of Christ or depart from him.”

He claimed civil partnerships “will remove ‘marital status’ from key legislation and public documentation and replace it with ‘civil status’, thus directly challenging the constitutional recognition that marriage is ‘a moral institution possessing inalienable and imprescriptible rights, antecedent and superior to all positive law.”

The Cardinal’s comments were rejected by gay rights advocates in the Republic.

Brian Sheehan, director of the Gay and Lesbian Equality Network, told the BBC:

“I understand the fears of people who are afraid that civil partnership will undermine marriages.

“But I think you can see from Northern Ireland and the UK that it is in the common good for people to be making lifelong commitments and the state providing a framework for that.”

The proposed legislation will grant gay and lesbian couples legal recognition in areas such as pensions, social security, property rights, tax, succession and the payment of maintenance.

It does not provide for legal recognition of the many same-sex couples, in particular women, who are parenting children together.

The government has ruled out gay marriage, claiming that it would require a change to the country’s constitution and a potentially divisive referendum.

Article 41 of the Irish constitution states:

“The State pledges itself to guard with special care the institution of marriage, on which the family is founded, and to protect it against attack.”

It does not give any definition of marriage itself, and critics and constitutional scholars argue it does not outlaw gay marriage.

Homosexuality was decriminalised in the Republic of Ireland in 1993.

Both discrimination and incitement to hatred on the grounds of sexual orientation are already illegal.