An action is usually thought to be in the public interest where it benefits society in some way. It is unclear though how many members of society must benefit before the action can be declared to be in the public interest. Some people would argue an action has to benefit every single member of society in order to be truly in the public interest. At the other extreme, any action can be in the public interest as long as it benefits some of the population and harms no one.
The extent to which an individual will make a disclosure "in the public interest" depends on their moral stance. In terms of Kohlberg this means that the individual will be at level three and is prepared to "blow the whistle" on unethical conduct.
