The Government introduced a bill to permit same-sex marriages into the ACT Legislative Assembly on Thursday morning.

The bill is expected to pass the 17-member Assembly in October with the support of all eight Labor members and Greens MLA Shane Rattenbury.

But it could be overturned by the federal parliament or subject to a High Court challenge.

Mr Corbell told a press conference that same-sex couples would be welcome to come to Canberra from interstate or overseas to get married, although their marriages may not necessarily be recognised in their home states.

"If people come to the ACT to get married because of this law, that really highlights why we need reform nationally and why we need changes to the law,'' he said.

"If there is so much demand for it, parliaments, politicians should be acting.''

Deputy Chief Minister Andrew Barr, who is gay and has a long-term partner, said he fought back tears while listening to Mr Corbell's speech.

"We're doing I think a really good thing today. It speaks to our values, it speaks to why we're in politics,'' Mr Barr said.

Earlier, Mr Corbell told the Assembly that said the bill followed on from earlier measures by the ACT Government to recognise the rights of people in same-sex couples, including the introduction of civil unions.

"Madam Speaker, this bill is about equality," Mr Corbell told the Assembly.

"It is a bill that says people in a same-sex relationship are able to have their love and commitment to each other legally recognised in the same way that people in a heterosexual relationship are able to through a legally-recognised marriage.

Mr Corbell said ministers of religion would not be required to officiate over same-sex weddings if they did not wish to do so.

The Attorney-General received a standing ovation from the public gallery after the debate was adjourned.

Opposition Leader Jeremy Hanson said the Canberra Liberals would not support the legislation when it is debated by the Assembly next month.

"Firstly, it's likely to be found unconstitutional and certainly I think everybody agrees it's going to be subject to a High Court challenge," he said.

"Secondly, it's just simply not the job of the ACT Assembly to be determining what is clearly controversial, national social reform.

"For those two reasons we won't be supporting it.

"Within the Liberal Party there are a range of views about same-sex marriage but what we all agree on is it shouldn't be debated by the Legislative Assembly of the ACT which is Australia's smallest jurisdiction."