Communications Minister Malcolm Turnbull says Australia is the "odd one out" on same-sex marriage among nations including the United Kingdom, New Zealand and Canada.

Ireland voted in favour of legalising gay marriage in a referendum at the weekend.

A number of Liberal MPs expect a partyroom debate around the issue this year.

Mr Turnbull, who supports marriage equality, said Australia was out of step with many Western nations on the issue.

"Most of the United States, Canada, New Zealand, South Africa, the United Kingdom and now Ireland, not to speak of a number of European countries [have legalised same sex marriage]," Mr Turnbull said.

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"If you think about, say, the British Commonwealth, if you think of the old Commonwealth, the Dominions, they are all now supporting same-sex marriage.

"Australia I suppose is the odd one out or is the one that has not yet turned its mind in a parliamentary sense to reviewing the law.

"The point is the context has dramatically changed and we can't be blind to that."

Mr Turnbull's comments follow South Australian Liberal senator Simon Birmingham saying he hoped the Coalition party room would consider the debate this year, and Queensland's Warren Entsch saying the party was "close" to confronting the issue.

Prime Minister Tony Abbott on Sunday reiterated his personal opposition to any change to marriage laws, but acknowledged the issue was important to many Australians.

"I've had informal discussions with the Prime Minister on this and where we would like to be on this," Mr Entsch told ABC News 24.

"We've had some discussions with colleagues and we'll be looking at some sort of a plan that I'm hoping I can put to the PM in the near future."

When asked if that plan was aimed at assessing the numbers before any potential vote, Mr Entsch said: "It's timing."

"We're not being that aggressive on this," he said, adding he believed there was growing support within the party.

"As time has progressed, you're seeing more and more people changing their views."

Debate should be held 'before next election'

Mr Entsch also said it was important frontbenchers too were allowed to vote as they wished.

"I'm looking more for a free vote rather than a conscience vote," he said.

"It's important. As a free vote it allows the executive also to be able to vote without having to resign their positions on the executive."

Senator Birmingham also said he believed there was a growing band of Liberals who would vote in favour of allowing homosexual people to marry.

"In the five years since I spoke out on this topic, I've been heartened by the number of colleagues who've indicated a change in position," he told Radio National.

He cited Victorian MP Josh Frydenberg and WA senator Dean Smith as two examples and said a number of other Liberals had indicated their support privately.

Senator Birmingham said the matter should be dealt with well ahead of the next election, which is due late next year.

Liberal Democratic senator David Leyonhjelm introduced a private members bill to legalise same-sex marriage last year but it remains on hold.