While Prime Minister Malcolm Turnbull said during the election campaign that he expected the plebiscite to be held by the end of the 2016, the Australian Electoral Commission provided advice to the government last week that "strongly recommended" against that timing.

"Mr Turnbull is willing to waste taxpayers' money and provide a platform for hate campaigns, all because he doesn't have the guts to put a vote to Parliament," Opposition Leader Bill Shorten said.

"Let's just get on with it. Parliament should do its job and deal with a marriage equality bill, with all parties afforded a free vote."

"Another broken promise by Malcolm Turnbull," Labor immigration spokesman Shayne Neumann said, repeating the opposition's warning that the campaign leading up to the plebiscite will be divisive and hurtful.

News Corp reported on Saturday night that the proposed question to be asked in a nationwide February vote, according to the advice to Special Minister of State Scott Ryan, would be: "Do you approve of a law to permit people of the same sex to marry?"

The Prime Minister's office said in a statement that the commitment to hold plebiscite "as soon as practicable" had not changed.

"The mechanics of the plebiscite, including the specific question and the timing, are subject to the usual cabinet processes. No decisions have as yet been made," the statement said.

Attorney-General George Brandis recently warned that that the compulsory vote may have to be held next year. Human Services Minister Alan Tudge said on Sunday that the AEC advice meant this was now likely.

Greens leader Richard Di Natale said he was unsurprised by the "delay tactic", calling the plebiscite a "pointless" sham that would be costly, divisive and ignored by some Coalition MPs anyway.

"Delays are the entire point of the Liberals' plebiscite ploy. They don't want to end discrimination in the law, they want to push it off to the never-never," Senator Di Natale said.

Same-sex marriage - and the details of how the debate should be resolved - remain a divisive proposition inside the Coalition. Some MPs have stated they will vote against changing the Marriage Act regardless of the plebiscite, causing others to ask "what's the point" of it.

As the plebiscite has firmed as the likely resolution, the debate has partly focused on whether the "yes" and "no" campaigns will be publicly funded.

Australian Marriage Equality, the leading campaigners for change, say they shouldn't be while the Australian Christian Lobby, the most vocal opponents of gay marriage, have demanded $15 million.

AME chair Alex Greenwich said on Sunday that they did not support a plebiscite but, "if one is being imposed", the question, process and timing need to be fair and devised with consultation.

"One immediate way the government can provide confidence in the process is by listening to the 10,000 Australians who have signed our petition to ensure no public funding is provided to either campaign," Greenwich said.

ACL managing director Lyle Shelton embraced the delay of the plebiscite, saying it was "no surprise" that 2016 was not feasible and the AEC needed more time for logistical reasons.

"It's important the process isn't rushed - from an administrative and consultation point of view. We need to get this right," he told Fairfax Media.

The yes camp has suffered divisions - leading to veteran LGBTI advocate Rodney Croome's departure from AME - over whether to accept the plebiscite or to persist with opposition to it and pursue a free vote in Parliament.

The national vote emerged as the Coalition's policy following an extended party room meeting last year under former prime minister Tony Abbott. Mr Turnbull, seeking the leadership in September, reportedly promised conservatives he would not change the government's position despite favouring a free vote.

Public support for same-sex marriage is consistently strong. A Fairfax-Ipsos poll last year showed 68 per cent in favour and 25 per cent opposed.