http://www.economist.com/node/18652037
The issue is that in India, it's illegal to both accept and give bribes. This prevents bribe givers from 1) blowing the whistle. 2) Admitting to others who want to convict the corrupt official that they gave him bribes.
"Kaushik Basu, the chief economic adviser to India’s finance ministry, suggests that this may be partly because the law treats both bribe-giving and bribe-taking as crimes. This makes it hard to blow the whistle on corrupt officials, because the bribe-giver has also broken the law. If he complains, he risks prosecution or, more likely, being asked for another bribe by the police. In a provocative paper based on game theory, Mr Basu argues for the legalisation of some kinds of bribe-giving. His proposal has instigated a furious debate in India, with television channels even assembling panels to discuss it."