New York-based Human Rights Watch, London-based Amnesty International and Brussels-based International Crisis Group last week accused the panel of a cover-up and refused an offer from Colombo to appear before it.
Peiris said in a speech to the International Institute for Strategic Studies, a leading think-tank based in London, that the rights groups had displayed a "most unattractive attitude."
"It smacks of an attitude that is almost colonial, patronising and condescending, the assumption being that other people must step in because Sri Lankans are unable to chart a course for their own future," he said.
The rights groups have long accused government forces of ordering civilians into a "no-fire zone" and shelling them in the final stages of fighting between government troops and Tamil Tiger separatist rebels in early 2009.
The United Nations has said that at least 7,000 ethnic Tamil civilians were killed in the final months of the conflict.
Rights groups say up to 30,000 civilia