There should be disclosure that the public official has disclosed it to someone outside of the government. Really, they're the ones who are supposed to be upholding the public trust and respecting the confidentiality of information, so they should pay the highest penalty.
If someone then uses it for their lobbying, the penalty should be very high, as well, because that's just a “who you know” system, people doing favours for you inside secretly. The penalty should be very high because it's so easy to hide it. If you are actually caught—there would be a huge likelihood that you wouldn't ever be caught—you should really pay a very high penalty for that.