(Transcript from World News Australia Radio)
A 2012 United Nations review concluded as many as 40,000 civilians were killed in the final months of Sri Lanka's civil war in 2009.
The UN review found credible allegations of war crimes by both government forces and the rebel Tamil Tigers.
Now, the International Crisis Group has issued a new report calling on the world to act to force an investigation into those matters and the restoration of the rule of law in the country.
The International Crisis Group has called for strong international action against Sri Lanka's government and is urging Australia and others to reject certain Sri Lankan diplomats.
Sri Lanka's High Commissioner to Australia, Thisara Samarasinghe, would fit into the group of diplomats the independent, non-governmental organisation wants barred.
The report comes almost four years after the end of the civil war in Sri Lanka spanning three decades and comes ahead of a meeting of the United Nations Human Rights Council.
The report, entitled 'Sri Lanka's Authoritarian Turn: The Need for International Action', says Sri Lanka has made no meaningful progress on reconciliation or accountability.
"The government has conducted no credible investigations into allegations of war crimes, disappearances or other serious human-rights violations. Rather than establish independent institutions for oversight and investigation, the government has, in effect, removed the last remnants of judicial independence through the impeachment of the chief justice."
The report calls on Australia and a range of other countries to look further into the war against the separatist Tamil Tigers, or LTTE, to:
"Investigate, gather and share evidence regarding alleged war crimes and human-rights abuses by government forces and the LTTE where possible."
"Refrain from accepting the diplomatic credentials of Sri Lankan military officers against whom there are credible allegations of serious crimes."
The High Commissioner to Australia, Thisara Samarasinghe, was cited in a 2011 submission by the International Commission of Jurists' Australian section.
It recommended the retired admiral be investigated for war crimes and crimes against humanity allegedly committed by the navy under his command in 2009.
Mr Samarasinghe has dismissed the International Crisis Group report, calling it one more report timed to come out before the Human Rights Council meeting each year.
"This is the action of people with a vested interest trying to give oxygen to defeated terrorists who are crying for a separate state from outside Sri Lanka."
The report says the Sri Lankan government is becoming increasingly authoritarian.
The International Crisis Group says the recent impeachment of the country's chief justice completes what it calls a constitutional coup.
The group says that began with an amendment in 2010 that revoked presidential term limits and the independence of government oversight bodies.
The Crisis Group says what it calls the government's attacks on the judiciary and political dissent threaten Sri Lanka's long-term stability and peace.
Thisara Samarasinghe says the claim is baseless and argues Sri Lanka has created stability in three-plus years as other troubled countries around the world have failed.
"Long-term stability and peace is very much established in Sri Lanka. After the trauma of conflict, death and destruction by terrorists -- a brutal terrorist organisation, which international leading countries termed invincible or most ruthless -- evidence and runs on the board,** Sri Lanka has put. Three years after defeating the terrorists, there has been no death or destruction from terrorist activities. You just have to compare this to the rest of the world."
Among other charges, the International Crisis Group says the Sri Lankan government has conducted no credible investigations into war-crimes and human-rights violations.
It says there has been no progress toward a lasting and fair constitutional settlement of the concerns of the country's ethnic Tamil minority through devolution of power.
The report claims the military still controls virtually all aspects of life in the Tamil-dominated north and has intimidated and sidelined the civilian administration.
The Crisis Group says more than 90-thousand people remain displaced in the north and east of the island, amid continued land seizures by the military with no effective right of appeal.
Australian Tamil Congress spokesman Bala Vigneswaran says that figure itself belies any idea the country is stable.
"We had nearly 360,000 people in camps immediately after the war. It shouldn't take more than three-and-a-half years for one-fourth of them still finding themselves in the wrong place. The Sri Lankan government has built a fence around the so-called high-security zone in the north particularly and the south as well. People are not allowed to leave, they're not allowed to go back to their traditional homeland, the place they lived for centuries and generations."
Mr Vigneswaran says he welcomes the Crisis Group's push for sanctions until the government restores the rule of law, investigates abuses and devolves power to areas where Tamils and Muslims are in a majority.
"We welcome this particular report by the International Crisis Group recommending the Sri Lankan government to listen to the international community and the UN Human Rights Council to come up with a stronger resolution, with a time frame, within a year. (The government) can't keep going, saying that 'we are improving and we are developing.'"
Christian clergy from northern Sri Lanka have also written a letter to the UN Human Rights Council, asking it to push for an independent international inquiry into alleged war atrocities.