The Tamil National Alliance legislators and other elected representatives met in the northern town of Vavuniya today and insisted on international intervention.
The call came despite the Sri Lankan government's continued policy of opposing an international hybrid court to probe the war crimes allegations.
"All Sri Lanka s obligations in terms of UN Human Rights Council Resolution...co- sponsored by the Sri Lankan Government, must be fully implemented. These obligations must be fulfilled under strict conditions, under the monitoring of an office of the UN High Commissioner for Human rights, which must be established in Sri Lanka," a statement said.
It said if the Sri Lankan Government fails to fulfil the obligations by way of an appropriate mechanism, the UN Human Rights Council must ensure that victims will receive the intended benefits of the fulfilment of such obligations, through international mechanisms.
Sri Lankan government has rejected the call for a hybrid court of local and international judges to probe alleged war crimes.
Sri Lanka faced three consecutive adverse UNHRC resolutions since 2012. In 2014, the resolution prescribed an international investigations into human rights abuses blamed on both the LTTE and the government troops.
Since the change of the government in January 2015, the rights body has shown leniency in allowing the new government more time to get its reconciliation house in order.
According to the UN figures, up to 40,000 civilians were killed by the security forces during Mahinda Rajapaksa's regime that brought an end to nearly three-decades long civil war in Sri Lanka with the defeat of LTTE in 2009.