Christian groups and the Catholic Church are lobbying the Federal Government to overturn the ACT's new laws for same-sex couples.

The Legislative Assembly passed a bill last week allowing gay couples to recognise their relationship with a legally binding civil ceremony.

But the Federal Government has the power to veto the new laws.

Last year it forced the ACT Government to water down a similar bill that formed the Territory's Civil Partnerships Act, arguing the arrangement was too similar to marriage.

The Commonwealth is yet to say if it will support the laws this time around and Federal Attorney-General Robert McClelland is examining the bill.

Catholic Archbishop of Canberra Mark Coleridge says the laws undermine marriage and he wants the Federal Government to step-in.

Attorney-General Simon Corbell says it is extraordinary that a church leader wants to undermine an elected parliament.

He says the Catholic Church is perpetuating discrimination against gay people.