Australians will all be invited to say "I do" on the question of same-sex marriage within a year.
And a national compulsory vote will be the only chance for people to speak or forever hold their peace, the attorney-general says.
George Brandis says a plebiscite is now the only way to legalise same-sex marriage after the coalition campaigned with that policy during the recent federal election.
He is consulting electoral commissioner Tom Rogers about how soon the national vote can be held before taking a submission on plans for the plebiscite to cabinet within weeks.
"The only way that in this parliament this issue can be progressed is through a plebiscite," Senator Brandis told ABC TV on Sunday.
"If it can't be done before the end of this year, it will certainly be done in the early part of next year."
His preference is for a compulsory vote on a question "as simple and as self-explanatory as possible" with the results reported for each electorate.
Cabinet will decide whether taxpayers should pay to promote arguments for and against same-sex marriage but Senator Brandis said any public money made available should be split equally.
Labor wants a free vote in the parliament rather than a plebiscite.
Opposition frontbencher Chris Bowen said as long as debate was focused on marriage equality, it was not dealing with the important matter of indigenous recognition in the constitution.
"We are focusing on the wrong issues here - the parliament should be deciding on marriage equality, the people should be deciding indigenous recognition in the constitution," he told Sky News.
"The nation can only deal with so many referendums, plebiscites at once."
Senator Brandis said he hoped Labor leader Bill Shorten would work with Prime Minister Malcolm Turnbull on the design of the plebiscite and the passage of enabling legislation.
"If Mr Shorten and the Labor Party can resist the temptation to try and use this as an opportunity to embarrass the government but rather ask themselves the question how are we most likely now to progress this issue to a satisfactory conclusion, we can arrive at a common point," he said.
Labor said there was absolutely no reason to count the results on an electorate-by-electorate basis, rather than just requiring a simple majority, and a decision to do that should worry everyone who supports same-sex marriage.
"This subterfuge allows conservative MPs opposed to same-sex marriage to defy a national 'yes' vote and vote against same-sex marriage, and justify that behaviour by pointing to the vote in their electorate," shadow attorney-general Mark Dreyfus said in a statement.
"It raises the spectre of a majority vote 'yes' on marriage equality and a failed vote in parliament."
