"The Government should act on this urgently. There is a threat to national security," said G L Peiris, former foreign minister and United People's Freedom Alliance (UPFA) MP.
He said the government should have convened a special cabinet meeting over the report.
The US State a Department report released last week had said Liberation Tigers of Tamil Eelam's international network and funding was intact.
It said that the defeated group was very much alive internationally.
Peiris alleged that recent Sri Lankan government action such as having talks with Tamil diaspora groups would encourage those who want to see the revival of the LTTE.
Foreign Minister Mangala Samaraweera had engaged diaspora groups in London for talks aimed at addressing the immediate needs of the war-affected Tamils.
