They staged a protest in the heart of Vavuniya town and handed over a related petition to the UN human rights chief Michelle Bachelet.
It asks Bachelet to inform the international community through her annual review that the government had intentionally avoided fulfilling the promises it gave in 2015.
It says the government is not going in the correct path towards accountability, justice, reconciliation and lasting peace, but is going backward.
In 2017, the UNHRC, TNA and others gave two years to the Sri Lankan government to implement the proposals it had agreed to with regard to war crimes and reconciliation.
The petition calls for alternative steps without giving any more time to fulfill the promises.