PM still confident about gay marriage vote

Malcolm Turnbull remains confident enabling legislation for a same-sex plebiscite will clear the Senate.

"Of course, of course," he told ABC radio on Tuesday, rejecting suggestions the government won't be able to win over sufficient crossbench support against opposition from Labor and the Greens.

"Experience tells me that you don't know what the numbers are until the votes are finally counted."

Mr Turnbull was later keen to highlight the Australian Christian Lobby's approval of Labor leader Bill Shorten's decision to oppose the plebiscite.

"He won their praise three years ago when he told them he'd support a plebiscite and now that he's decided to oppose one they've thanked him for postponing the day when gay marriage can occur," the prime minister told reporters in Parliament House.

Mr Turnbull said he would continue attempts to convince crossbench senators and even Mr Shorten to support the plebiscite's enabling legislation.