He told Daily Mirror that Sri Lanka should avoid making fresh representations to the UNHRC as it had already co-sponsored a resolution.
"If Sri Lanka keeps avoiding its international commitments, it will soon lose its legitimacy and be termed a failed state. Those who suffered during the war, need answers as to what happened to their loved ones. It has to be probed," Mr. Sampanthan said.
The TNA is awaiting an invitation for talks with President Gotabaya Rajapaksa and Prime Minister Mahinda Rajapaksa where it hopes to raise these concerns.
Sri Lanka's new interim Cabinet said earlier this week that it will look at making a fresh presentation to the UNHRC which will lay down all the facts and figures of the atrocities committed by the LTTE during the 30-year armed conflict.
The government hopes to urge the United Nations to probe the island's war in its entirety and not only during the final stages, while Foreign Minister Dinesh Gunawardena is likely to hold talks with the UNHRC, in the coming weeks over the matter.
The government claimed that the UNHRC Resolution 30/1 which Sri Lanka co-sponsored in 2015 titled "Promoting Reconciliation, Accountability and Human Rights in Sri Lanka” had been solely submitted by former minister Mangala Samaraweera without the approval of the former Cabinet, Parliament or the advice of the AG's Department and this resolution would now be reviewed.