THE federal government will help Australian same-sex couples marry in countries where gay marriage is legal by issuing them with documents currently available only to heterosexuals.

In several nations that allow gay marriage, including Portugal, Spain, Norway and South Africa, a person must produce a Certificate of No Impediment, which proves they are at least 18, unmarried and that there is no other barrier to them taking part in a marriage ceremony.

"This important change will allow same-sex couples to take part in overseas marriage ceremonies, and be considered married according to the laws of that country" ... Attorney-General, Nicola Roxon. Credit:Andrew Sheargold

The Attorney-General, Nicola Roxon, will announce today that from February 1 same-sex couples will be able to apply for the certificates.

''This important change will allow same-sex couples to take part in overseas marriage ceremonies, and be considered married according to the laws of that country,'' Ms Roxon said.