This year, during the Sydney Gay and Lesbian Mardi Gras, campaigners raised $40,000 in one night to take their fight for reform to the electorates of individual federal MPs.

It is 10 years on Wednesday since the Howard government, with Labor's support, changed the federal Marriage Act to define marriage as being between a man and a woman.

Mr Greenwich, the former director of Australian Marriage Equality and now the independent NSW MP for Sydney, said community sentiment had clearly swung in support of same-sex marriage since that time, and there had been a steady, albeit slower, change in political attitudes.

''We've gone from having the Greens and the Democrats as the only supporters of reform to working our way through the Labor Party and now the Coalition,'' he said.

''It hasn't been easy.''

To mark a decade since the change, Mr Greenwich will introduce a bill in the NSW parliament on Wednesday that would grant de facto status to same-sex couples from that state who marry overseas.

Former prime minister John Howard's changes to the marriage act were prompted by two same-sex Australian couples who sought legal recognition for their marriages in Australia after marrying in Canada.

A Greens bill that would allow overseas same-sex marriages to be recognised as marriages in Australia is also before a federal Senate inquiry, with hearings to begin next week.

If the Greens bill is passed by the federal parliament, Greens senator Sarah Hanson-Young said it would be a ''small step that will send a positive message to all gay and lesbian Australians''.

A decade ago, polls showed community support for same-sex marriage was just 38 per cent.

A Crosby Textor poll taken in June found that figure has nearly doubled to 72 per cent, while nearly 80 per cent of swing voters favour a change in the law.

Libertarian NSW senator David Leyonhjelm is preparing a private member's bill to legalise same-sex marriage, but has said he will not bring it to a vote until it has a good chance of success and Coalition MPs are granted a conscience vote.

Despite the positive developments for same-sex couples, marriage equality advocates said the past 10 years had been filled with sadness.

Australian Marriage Equality said while the debate around same-sex marriage was frequently shown through stories of ''youthful, hopeful, exuberant couples'', there were many older couples who had endured decades of prejudice and were looking for a chance to share ''newfound dignity'', but were running out of time.

''Partners who wished to marry have died, couples who wanted to marry at home have been forced overseas to wed, and too many parliamentary votes have failed because MPs were forced to vote along party lines,'' the group's national director, Rodney Croome, said.

Opposition Leader Bill Shorten acknowledged that his own views on same-sex marriage had changed in the past 10 years ''like a lot of people in the community''.

''Change like this never happens overnight but I'm confident that one day soon gay and lesbian Australians will be afforded the same right to marry as other Australians,'' he said.