Sri Lanka's main minority Tamil party demanded Friday that foreign judges be included in a special court to investigate war crimes, a day after the UN again granted Colombo more time for a much-delayed probe.
Government troops have been accused of killing at least 40,000 ethnic Tamil civilians in the final months of the island nation's 37-year civil war in 2009. No one has been prosecuted for war crimes in the decade since.
With no measurable progress, the UN Human Rights Council in Geneva on Thursday gave Sri Lanka two more years to set up a credible investigation, the second time it has been given an extension.
The probe is meant to include a special "hybrid" court involving both local and foreign judges and prosecutors.
But on Wednesday in Geneva, Sri Lankan foreign minister Tilak Marapana said the country's constitution did not allow foreign judges.
This prompted uproar from Tamil National Alliance (TNA), with lawmaker Mathiaparanan Abraham Sumanthiran threatening on Friday to report Sri Lanka to the International Criminal Court (ICC).
"If the government does not agree to a hybrid court, Sri Lanka will have to face a tribunal which will be entirely international," Sumanthiran said in parliament.
He said Tamils, who were the most affected by the separatist war that claimed over 100,000 lives, will not accept an accountability mechanism that did not involve outsiders.
"The state of Sri Lanka cannot be an independent arbiter," he said.
Colombo's no-holds-barred military campaign wiped out the leadership of Tamil Tiger rebels and ended the war in May 2009.
UN rights chief Michelle Bachelet warned this week that Sri Lanka risked slipping back into conflict unless it addressed the "worst crimes" of the war.
She noted that Colombo was yet to set up the special judicial mechanism as promised four years ago.