The delegation, aimed at showing solidarity with the Syrian people and opposing Western military intervention, reportedly included WikiLeaks founder Julian Assange's father John Shipton, CEO of the political party.
The group met with Assad on December 23, according to a post on the Syrian president's Twitter feed.
The visit triggered a furore when revealed in Australia on Tuesday, with the centre-left Labor opposition describing it as "extraordinary" and "irresponsible".
"The Assad regime has been widely and correctly criticized around the world," said Labor frontbencher Chris Bowen.
"For an Australian political party to think it's sensible to go and have discussions and try and provide some legitimacy, is something I think which they have to explain," Bowen said.

The WikiLeaks Party was founded by Assange as part of his failed campaign for election to Australia's parliament this year, but is distinct from the amorphous whistleblowing group.

WikiLeaks distanced itself from the delegation when asked about it on Tuesday. "Peace brokering a good idea, but obvious meeting would be spun without care. Did not know or approve," it said on its official Twitter feed.

According to The Australian newspaper, the delegation included Shipton and WikiLeaks national council member Gail Malone, as well as Sydney university academic Tim Anderson and refugee activist Jamal Daoud.
Shipton announced plans to set up a WikiLeaks Party office in Damascus in a show of solidarity with ordinary Syrians, The Australian said.
The WikiLeaks Party said a "formal report from the fact finding delegation will be published once the delegates return to Australia", in a brief statement on its Twitter feed.

In a December 22 website post announcing it would take part in the "solidarity delegation", the WikiLeaks Party said the visit was to show opposition to violence and Western military intervention.
"The WikiLeaks Party was the first party in Australia to warn of the deadly consequences of any Western military intervention in Syria," the post said.
"It went further by questioning the credibility of the excuses of such intervention based on unsubstantiated reports of the Syrian Army's use of chemical weapons against Syrian civilians.
"The same excuses", which turned out to be "no more than fabrications and lies" had been used to justify the US-led war in Iraq, the party said.


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