Sydney Archdiocese Marriage and Family Office director Chris Meney (pictured with his family) said there are many benefits to society due to exclusive heterosexual unions including children, supportive and safe environments to raise children in and a biologically connection to the child.
Mr Meney added that a substantial social benefit results when marriage between a man and a woman is the norm.
However, PM Kevin Rudd says he will not block the ACT Government's plans to legalise same-sex civil unions.
"Such unions also provide a mechanism for effectively connecting children to their fathers, a longing of every child, and also for ensuring a fairer distribution of the parenting burden," Mr Meney said.
"Nation states have regularly supported exclusive heterosexual unions because, as a type, these unions have the capacity to contribute to the society in an essential and substantial way.
"Children may seem optional for spouses; they are not optional for societies. It is not sexual orientation or even simple co-dependency that forms the basis for according married couples a special status under the law," he said.
This latest attempt to legalising same-sex unions is the third time the ACT has tried to implement its Civil Partnerships Bill, following two attempts to pass the draft laws while the Howard Government was in power.
"Retaining the current special status for heterosexual marriage over other types of unions is vital."
Same-sex unions threat to society (Catholic Weekly 16/12/07)
LINKS (not necessarily endorsed by Church Resources)
Marriage & Family Office, Archdiocese of Sydney
Pope speaks out against gay marriage (CathNews 11/06/03)
500,000 march against same-sex marriage (CathNews 20/06/05)
Cardinals attack Spanish Bill on same-sex marriage (CathNews 27/4/05)
Adelaide Archbishop backs equal rights for gay couples (CathNews 17/3/05)
Bishop has 'no difficulty' with civil recognition for gay couples (CathNews 27/10/04)
NZ gay law 'to make moral wasteland' (CathNews 29/6/04)
Bishop says gay marriage advocates flattering "real" marriage (CathNews 3/3/04)
Boston archbishop supports gay couples to protect children (CathNews 27/10/03)
Pope speaks out against gay marriage (CathNews 11/6/03)
Judge apologises to gay activists on behalf of Catholic Church (CathNews 3/2/03)
18 Dec 2007