Tamil National Alliance (TNA) legislator Suresh Premachandran said that his party would push their case when the UN Human Rights Council meets next March in Geneva.
The party would also brief the international and diplomatic communities on the need to conduct an independent investigation.
Reacting to the TNA's plan, government spokesman and Information Minister Keheliya Rambukwella dismissed it as the TNA's separatist intent in the current post-conflict phase.
"They must try to resolve problems within the country rather than going international against the state," he said.
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Sri Lanka has been censured by two successive UNHRC resolutions which demanded speedier action to achieve reconciliation with the island's Tamil minority.
The resolutions, moved by the US and backed by India, urged Sri Lanka to show results in full implementation of recommendations of its own reconciliation arm, the Lessons Learnt and Reconciliation Commission (LLRC).
Sri Lanka is expected to face its third successive resolution criticising its human rights record at the UNHRC meet in March.
The government however maintains that a considerable number of recommendations have already been implemented while some of them need more time for implementation.