The Prime Minister, John Howard, says the Federal Government won't be softening its opposition to same-sex unions.
The government wants to introduce legislation to block Canberra's proposed laws, which allow the registration of civil unions, giving gay and lesbian couples the same rights as heterosexuals.
Mr Howard says the ACT laws are an attempt to undermine federal laws introduced in 2004, defining a marriage only as a union between a man and a woman.
The ACT legislation however, does not use the word "marriage".