Prime Minister Tony Abbott has been asked to raise the issue of human rights when he visits Sri Lanka this week, after an Australian Greens motion succeeded in the Senate.
The motion, which was passed unopposed, demands Mr Abbott "raise the matter" with Sri Lankan President Mahinda Rajapaksa of an independent investigation into allegations of human rights violations.
Mr Abbott is due to leave Australia on Thursday to attend a Commonwealth Heads of Government Meeting (CHOGM) in Colombo on Friday.
Greens Senator Lee Rhiannon said Mr Abbott needed to listen to the parliament "and commit to at least fulfilling this basic request".
"British Prime Minister David Cameron has publicly stated he will be meeting with the Sri Lankan president and calling for a full, independent investigation into alleged war crimes," she said in a statement.
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The prime ministers of Canada and India are boycotting the CHOGM, which will be opened by Prince Charles.
Other leaders, including Mr Cameron, have resisted domestic political pressure not to make the trip, arguing it is better to engage the island nation rather than isolate it.
Earlier this week, Mr Abbott said he would urge Sri Lanka to "respect everyone's rights".
However, he also acknowledged progress had been made and Australia needed to maintain the "best possible relations" with Sri Lanka, given its co-operation in taking back would-be asylum seekers who arrived in Australia on boats.
