Prime Minister Manmohan Singh today directed the CBI, which is investigating high-profile 2G and CWG scams, to thoroughly investigate these cases, produce quick results and act without fear to bring to book those guilty.

"The handling of these cases constitutes a litmus test for you," he told the top brass of the CBI at a function to inaugurate the new CBI headquarters, although he did not specifically refer to the 2G or Commonwealth scams in which the agency has arrested top corporate honchos as well as sacked chairman of CWG Organising Committee Suresh Kalmadi and former Telecom Minister A Raja.

Describing these as "high-profile" cases, the PM said in a forthright address that "the CBI should act without fear or favour and bring to book all those who are guilty, irrespective of their position or status.

"I would advise the CBI to put your heads down and work hard, away from the media glare, to ensure early resolution of these cases," the Prime Minister said.

Singh refereed to his address at the Civil Services Week during which he had spoken about the problem of corruption and the growing "impatience of our people to see quick action for tackling it".

"The CBI is today investigating many high profile cases of corruption that have attracted a great deal of public attention," he said, adding "what is expected of you is thorough investigation, fair action and quick results."

The Prime Minister also had a word of caution for the sleuths, saying that it was important for the CBI to ensure that its judgement always remains rooted in "hard evidence and is not influenced by extraneous factors".

"Ours is an open and free society. There will be many views and opinions on all issues. The CBI has to be sensitive to these but it has always to do what is right and correct," he said and added that there was only one "guiding beacon" -- only one gold standard and that is the law of the land.

"Whoever transgresses it, however mighty, he has to be brought to book. At the same time, CBI has to avoid harassment to those who act in good faith in the discharge of their duties."

Singh cautioned the CBI that there should be no vendetta, no witch-hunt and no harassment of the innocent. "There should be no apprehension of punitive action for bona fide mistakes as we cannot afford an environment that breeds fear, inaction and indecision."