Prime Minister Dr Manmohan Singh today said the CBI should act without fear or favour and bring all those guilty to book irrespective of their positions.Speaking after inaugurating the new CBI headquarters in New Delhi, Dr. Singh said the handling of high profile cases constituted a litmus test for CBI officers. He said the CBI hasd set a benchmark for other investigating agencies in the country to emulate but there was room for improvement.The Prime Minister said the Government was committed to provide manpower, finances and technology that the premier investigating agency requires. He said the Centre was also committed to give the bureau the necessary independence and operational flexibility. Dr. Singh said the Government had decided to establish 71 additional special courts for the CBI, of which 64 have been sanctioned but only 16 are operational.Singh said over the years the CBI had evolved as the premier investigating agency of the country and there was a loud clamour for investigations to be handed over to it.Minister of State V Narayansamy said the Government was committed to zero tolerance on corruption. He also said work was on to upgrade the resource base of the CBI.