Malcolm Turnbull has taken another thinly-veiled swipe at Scott Morrison, this time over climate change.
Mr Turnbull has told a private function of moderate factional allies they must be "loud Australians" on climate policies.
The declaration has been interpreted as a direct rebuke of Mr Morrison, who credits "quiet Australians" for his federal election win.
The prime minister hit back at his predecessor in federal parliament on Monday.
"The government is implementing the policies on emission reductions that began under prime minister Turnbull," he said.
"Emissions are now lower than they were when the coalition government came to office, and then have declined each year since 2016-17."
Mr Turnbull reportedly told former colleagues, including two cabinet ministers, the government's "incoherent" climate change policies were holding back billions of dollars worth of investment.
He called on "real liberals" to take effective action on climate change.
"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 night, the Daily Telegraph reports.
"We have to be loud Australians and stand up for our values and get the outcomes, deliver the government and the policies Australians deserve."
Some in the audience were quick to pick up on the swipe.
"It was hard not to read it as a dig at Morrison," one attendee told the newspaper.
Senior cabinet minister Simon Birmingham was at the gathering but did not hear the speech.
Senator Birmingham said the government was already taking strong action on climate change.
"What we have to do as a government is absolutely to make sure people better understand the policies we are pursuing," he told ABC radio.
"I am trying, speaking to you right now, to make sure that we are selling in a coherent way those strong policies and it is up to all members of the government to do that."
Communications Minister Paul Fletcher and incoming US ambassador Arthur Sinodinos also attended the speech.
Mr Turnbull's latest intervention comes just days after he criticised the prime minister for contacting the NSW police chief about a fraud investigation involving Energy Minister Angus Taylor.
Mr Turnbull said it was critically important for police inquiries - particularly those involving politicians - to be free from political influence.
"I am sure the call that the prime minister made to the NSW police commissioner was innocuous, but it would have been much better had it not been made," he said last week.