Foreign Minister Kevin Rudd is under fire for failing to respond to a Sri Lankan government report on that country's civil war, despite repeatedly promising he would.

The Lessons Learnt and Reconciliation Commission (LLRC) - set up by Sri Lankan President Mahinda Rajapaksa in May 2010 - released its long-awaited report into the 26-year conflict two months ago.

The Canadian and UK governments have been among critics of the report, saying it does not adequately address persistent allegations that both sides of the conflict committed war crimes.

Rights groups say the report is a whitewash and have intensified calls for an independent investigation into the war, particularly Colombo's final bloody offensive against the Tamil Tigers in 2009.

Mr. Rudd last year said the government wanted to read the LLRC's report before assessing the need for further probes.

But since the report's release he has been silent.

The Australian Greens on Thursday criticised the delay.

"Foreign Minister Kevin Rudd has waived aside growing international concern about Sri Lankan war crimes for months citing the need to wait for the LLRC report," Greens Senator Lee Rhiannon told reporters in Canberra.

"It is almost two months since the LLRC report was released, yet Mr. Rudd remains tight-lipped."

Senator Rhiannon believes the government's cooperation with Colombo on stopping asylum-seeker boats could be one reason for the delay.

But the time for diplomatic tip-toeing was past, she said.

"War crimes and crimes against humanity were committed in our region, and we have a responsibility to speak out against it and ensure those that were responsible are held to account."

The government later said it was still completing its assessment of the report.

A spokesperson for Mr. Rudd said the government would "make its views known shortly."

"The government has consistently urged Sri Lanka to investigate all allegations of crimes committed by both sides to the conflict," the spokesperson said. (Source: AAP)