New Delhi, Aug 26 - High-level corruption should be pursued aggressively, Prime Minister Manmohan Singh said Wednesday while telling the Central Bureau of Investigation (CBI) that the 'big fish' must not escape punishment.

'High-level corruption should be pursued aggressively. There is a pervasive feeling that while petty cases get tackled quickly, the big fish escape punishment. This has to change. Rapid, fair and accurate investigation of allegations of corruption in high places should remain your utmost priority,' Manmohan Singh said while addressing CBI officers at the spacious Vigyan Bhavan here.

'The nation expects you to act firmly, swiftly and without fear or favour. And you have the constitutional and legal protection and safeguards to do so.'

Emphasising that there was 'no single remedy' for fighting corruption, the prime minister said the battle against it has to be 'fought at many levels'.

'There is no single remedy for fighting corruption.