"There's only one thing left to do," he said, choking up slightly. "Ryan Patrick Bolger, will you marry me?"

It was, in all likelihood, the first marriage proposal to be made on the floor of Parliament. And the answer came back fast and loud: "Yes."

The word has been heard ad nauseam in recent weeks, but rarely in a context so personal. The Melbourne pair have considered themselves fiances for years, and now, as same-sex marriage enters the final stretch of parliamentary debate, their long-awaited wedding day finally nears.

The joyous moment followed a fiery speech in which Mr Wilson castigated the Liberal Party over its tortured path toward enabling marriage equality, particularly those who insisted on putting same-sex marriage to a popular vote.

"They have been prepared to discard numerous principles - parliamentary supremacy, representative democracy, our party's tradition of a free vote, fiscal prudence and free speech," Mr Wilson said.​

"I take great pride in being able to say at every single occasion I stood up and defended our institutions, traditions and freedoms ahead of the politics of the day.

The Liberal Party should "reflect on this debate and learn from it", Mr Wilson said. 

"Some of us are liberals, real liberals, living [Robert] Menzies' address to his 1965 federal council that we are not the party of the past, not the conservative party dying hard on the last barricade, but one with a lively mind and a forward-looking heart," he said.

The legalisation of same-sex marriage would make lesbian, gay, bisexual, transgender and intersex Australians "full citizens for the first time", Mr Wilson said.

He told of his "haunting doubt" while struggling with his sexuality as a teenager, and his ultimate resolution at 18 years of age not to "give in" to the stigma around homosexuality.

"This bill rams a stake into the heart of that stigma and its legacy," he declared.

Later, the official House of Representatives Twitter account posted that after examining Hansard records, it believed Mr Wilson was the first person ever to propose on the floor of the House.

Other gay Liberal MPs, including Trent Zimmerman and Trevor Evans, spoke in favour of the bill on Monday morning after it was introduced by LGBTI ally and long-standing gay rights campaigner in the Liberal Party, Warren Entsch.

Debate on the bill is expected to conclude by Wednesday or Thursday and pass easily. 

The story Liberal MP Tim Wilson proposes to partner Ryan Bolger on the floor of Parliament was originally published on The Sydney Morning Herald.