The controversy - which has entered its third straight day - originated from Anthony Albanese's appearance on podcast that aired in July, when he mentioned Japanese Prime Minister Sanae Takaichi gifted him crown melons during a recent visit to Australia.
"She brought two and they're beautiful," he said while making a gesture with both hands in front of his chest.
He has repeatedly rejected calls to apologise over the incident.
Coverage of the comments prompted a letter from Tokyo to Canberra, which said there had been ''sensationalised reporting in the Australian media'' about the interview.
It was leaked to several media outlets.
No action would be taken by the Japanese government over the incident, the letter said.
Coalition frontbenchers Ted O'Brien and James Paterson wrote to the Australian Federal Police on Tuesday and requested an investigation into how the leak occurred.
Opposition Leader Angus Taylor and other Liberal figures repeatedly demanded the prime minister apologise to Ms Takaichi.
"Even if they were a gaffe, they were wrong and there are serious consequences from the unserious podcast that the prime minister hosted in The Lodge," Mr Taylor said.
Mr Albanese spent much of Wednesday rejecting the criticism.
"The relationship between Australia and Japan has never been stronger," he said in response to one of several parliamentary questions.
"We take our relationship seriously, including our obligations for engagement, including with Japan."
He described the opposition's AFP referral as "a political stunt", but said he was confident police would do their work as an independent agency.
In Japan, reporting on the incident has been far more subdued than the Australian media frenzy.
However, a Japanese correspondent covering Australia told AAP the melon comments had gained traction on social media in his home country.
There were concerns about the potential sexualisation of a leader, said the reporter, who did not wish to be identified.
Most politicians and journalists in Japan had not given airtime to so-called "melongate" and were not concerned about its impact on bilateral relations, they said.
Japan's parliament, known as the Diet, is in recess.
Mr Albanese was even on the wrong end of a jibe from his own party member in Speaker Milton Dick.
"When I make mistakes, I own up to them," Mr Dick quipped in parliament.
One Nation leader Pauline Hanson impersonated the prime minister's hand gestures while demanding Mr Albanese declare the melons on his register of interests.
The precise number of melons gifted was of concern, she said.
"Now we're hearing he had four melons and he ate two and then he realised," Senator Hanson said.
"Now he says he's got four. He's always lied to the public."
The melons, which AAP confirmed were valued at $400, fell under the expense threshold for reporting so were not recorded on the prime minister's official gift log.
A number of Labor politicians came to their leader's aid, saying the podcast comments had been taken out of context.
Housing Minister Clare O'Neil said the Liberals had "absolutely lost the plot" with their calls for an AFP probe.
"My personal view is that the Australian Federal Police should be allowed to focus on their job, which is keeping Australians safe and fighting crime for Australians," she said.
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