"It is not the business of the investigative agency to lay down a rule of conduct; nor is it the business of the investigating agency to presume a rule of conduct," the former home minister said.
Chidambaram said the investigative agency must confine itself to the question whether there has been a violation of a laid-down rule of conduct.
"Even where a rule has been prescribed, there is a policy behind that rule. It is not the business of the investigative agency to question the wisdom of that policy or to suggest a different policy that would be better in the view of the investigating agency," he said.
Last month, the Prime Minister's Office came under the lens after the CBI filed a fresh set of charges on the coal allocation case, this time finding fault with the actions of then coal secretary P.C. Parakh in allocating some blocks to private player Hindalco.
Both Parakh and the Prime Minister's Office clarified later that the decision on the award of coal block to Hindalco, taken in 2004-05, was fair and taken in good faith and no ulterior motive was required to be attributed on the matter.
Chidambaram also rejected allegations of the central government's interference in the investigative agency's working.
