There was no shortage of cake-related puns at Parliament House when senators arrived for the final day of the sitting week.
Labor's Sam Dastyari came armed with a three-tiered wedding cake in support of same-sex marriage.
"I'm baking the vote here," he told bemused reporters.
"I don't think you could have designed a worse system for disenfranchising young people than saying you're going to have a postal ballot vote system that is so last century that it's mind boggling."
In between handing out cookies and slices of cake, Senator Dastyari highlighted two flaws: not opening the ballot to online voting and limiting participation to those over 18.
"In a non-binding poll, why aren't 16 and 17-year-old Australians also being enfranchised in this process?" he asked.
Senator Dastyari said major parties had a responsibility to get young people involved and deplored former prime minister John Howard's decision to campaign for a 'no' vote.
"This is Night at the Museum. This is a blast from the past," he said.
Deputy Prime Minister Barnaby Joyce is confident anyone who wants to participate will do just that.
"I think young people are just as competent as any other person," he said. "If they want to be part of the vote, they'll be part of it."
Greens senator Peter Whish-Wilson said his party, which is talking to marriage equality advocates about a possible boycott of the ballot, was concerned about young people being enrolled in time.
Liberal Democrats David Leyonhjelm dismissed as "bullshit" former prime minister Tony Abbott's argument that voting 'no' would stop political correctness in its tracks.
"The postal plebiscite is not about political correctness. It's not about free speech. It's about same-sex marriage."