'Decent' debate about gay marriage: PM

Prime Minister Tony Abbott says there will be a "very full, frank and candid and decent" debate inside the Liberal partyroom about legalising same-sex marriage.

Mr Abbott was responding to a Labor move to introduce a private member's bill to parliament next week with a likely vote later in the year.

"It is an issue where decent people can differ," the prime minister told reporters in Canberra on Wednesday.

At some point, nearer to a vote, Liberal MPs would debate the issue in their party room.

"I'm sure at that time we'll have a very full and frank and candid and decent debate," Mr Abbott said.