The government said New York-based Human Rights Watch lacked evidence to backup its allegations of military support for enlisting child soldiers, relying instead on "unsubstantiated" claims from a UN official.
Human Rights Watch released a 100-page report on Wednesday accusing the military of collaborating with a breakaway rebel faction to recruit children in its battle against main rebel group the Liberation Tigers of Tamil Eelam (LTTE).
The report cited UN special representative Allan Rock who accused in November the breakaway faction known as the "Karuna group" of rounding up youngsters to be enlisted.
The government said in a statement there were "inherent weaknesses" in the approaches and procedures used by Rock.
"Statements implicating either the government or the government security forces in child recruitment activities remain unsubstantiated," it said.
However the government said it would "engage an independent and impartial process to investigate the allegations made.
"This process will be conducted to determine the facts," it said, without revealing who would conduct the inquiry or when it would commence.
The government promised a similar probe in November after Rock's