The Sri Lankan High Commission in London said images shown on Channel 4 on Tuesday night had not been verified as genuine and the disturbing footage could incite hatred among Sri Lankan communities.
However, it added that a local panel known as the Lessons Learnt and Reconciliation Commission (LLRC) was ready to take note of the claims and take remedial legal action.
"If the allegations levelled by Channel 4 or any other party are found to be genuine, the LLRC will take due note of all such cases and remedial measures will be taken by way of legal sanctions," the statement said.
There was no immediate comment from the government in Colombo on Wednesday, which is a religious holiday marking the arrival of Buddhism in the island 2,300 years ago.
But ministers have repeatedly denied all war crimes allegations.
The state-run Daily News repeated the defence ministry claim that Channel 4 footage was "fake" but said the government must show "rapid progress in meeting the just needs