On ABC's AM, Twomey also questioned the method of appropriating funds, noting that a finance minister's advance "has to be for some kind of emergency that's unforeseen [and] here we have an issue that has been foreseen and previously there had been allocations for it in the budget".
"This is simply about whether every loving relationship should be treated equally before the law".
If that fails, the government believes it will be able to hold a voluntary, non-binding postal plebiscite before the end of the year on the issue.
Mr Abbott opposed the postal plebiscite in the party rom, saying its should be a national compulsory vote or nothing.
"Democracy is something that is a gift".
"There is only one reason why this failure to deal with marriage equality has dragged on as long as it has - it is because of the complete failure of leadership and weakness of the prime minister", opposition leader Bill Shorten said.
In a powerful speech in the Senate, Senator Wong urged the Turnbull government to forgo an expensive and divisive public vote.
"My experience... is that most Australians are far more generous spirited, have a lot more honour than numerous people who are arguing this in the parliament from the other side", Wong told Sky News. "I know what a hard debate is like".
"It's a pretty low way to approach this debate".
The traditional plebiscite would cost up to $170 million.