Liberal Party members need to be "loud Australians" on climate change, former prime minister Malcolm Turnbull says.

Mr Turnbull told a private function of moderate factional allies the government's current climate policies were incoherent, The Daily Telegraph reports.

"It was hard not to read it as a dig at (Prime Minister Scott) Morrison," one attendee told the tabloid on Monday.

Mr Turnbull also warned the party against pursuing authoritarian populism, as seen in the United States with Donald Trump and the United Kingdom with Boris Johnson.

"So the real challenge for the moderates for all of us, for the liberals in the Liberal Party is the one thing we cannot be, now or ever, is quiet Australians," he said on Thursday.

"We have to be loud Australians and stand up for our values and get the outcomes, deliver the government and the policies Australians deserve."

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Mr Turnbull also defended his record, pointing to same-sex marriage, trade agreements and national security laws passed during his tenure.

In the audience were senior government minister's Simon Birmingham and Paul Fletcher, as well as Arthur Sinodinos, the soon-to-be ambassador to the US.